DAIRY   CHEMISTRY 


DAIRY  CHEMISTRY 


BY 


HARRY  SNYDER,  B.S. 

PROFESSOR  OF  AGRICULTURAL   CHEMISTRY,    UNIVERSITY  OF 

MINNESOTA,   AND  CHEMIST  OF  THE  MINNESOTA 

EXPERIMENT   STATION 


Neto 
THE    MACMILLAN   COMPANY 

LONDON:  MACMILLAN  &  CO.,  LTD. 
1914 

All  rights  reserved 


COPYRIGHT,  1905, 
BY  THE  MACMILLAN  COMPANY. 


Set  up  and  electrotyped.     Published  December,  1905. 
Reprinted  January,  1907  ;  February,  1911 ;  March,  1914. 


NorfoooD  }3rrss 

J.  8.  Gushing  &  Co.  —  Berwick  &  Smith  Co. 
Norwood,  Mass.,  U.S.A. 


5F 


PREFACE 

THIS  work  is  the  outgrowth  of  a  course  of  lec- 
tures given  by  the  author  for  a  number  of  years  to 
the  students  of  the  Agricultural  Department  of  the 
University  of  Minnesota.  During  recent  years 
material  progress  has  been  made  in  dairying,  and 
in  writing  this  book  it  has  been  the  aim  briefly 
to  incorporate  the  results  of  the  more  important 
investigations  on  the  subject.  In  the  prepara- 
tion of  the  work  extensive  use  has  been  made 
of  the  bulletins  and  reports  of  the  Agricultural 
Experiment  Stations  of  the  United  States  and  of 
other  works  on  the  subject.  It  is  the  aim  to  present 
in  as  concise  a  form  as  possible  the  principal  changes 
that  take  place  in  the  handling  of  milk  and  in  its 
manufacture  into  butter  and  cheese.  While  our 
present  knowledge  of  some  phases  of  the  subject  is 
incomplete,  there  are  many  facts  that  are  known 
and  have  been  found  very  useful  as  an  aid  in  the 
production  of  dairy  products  of  the  highest  sanitary 
and  market  value. 

It  is  believed  that  a  knowledge  of  the   general 


vi  PREFACE 

principles  of  dairy  chemistry  will  be  found  useful 
alike  to  the  farmer,  to  the  factoryman,  and  to  the 
consumer,  and  this  work  has  been  prepared  with 
the  view  of  giving  information  to  the  layman  rather 
than  to  the  scientist. 

HARRY  SNYDER. 

COLLEGE  OF  AGRICULTURE, 
UNIVERSITY  OF  MINNESOTA, 
ST.  ANTHONY  PARK,  MINNESOTA, 
December  1,  1905. 


CONTENTS 

CHAPTER  I 
THE  COMPOSITION  OF  MILK 

PAGE 

Complexity  of  composition  ;  Milk  serum  ;  Milk  solids  ;  Milk 
fais ;  Casein  ;  Albumin  ;  Milk'  augar  ;  Ash  ;  Variations 
in  composition  of  milk;  Percentage  composition,  and 
total  yields ;  First  or  fore  milk  and  strippings ;  Milk 
serum,  Constancy  of  its  composition  ....  1 

CHAPTER  II 
MILK  TESTING 

Importance  of  milk  testing  ;  Reliability  of  the  Babcock  test ; 
Sampling  milk  ;  Measuring  milk  with  the  pipette  ;  Mak- 
ing the  test ;  Reading  the  fat ;  Calibration  of  test  bottles  ; 
Speeding  the  machine  ;  Centrifugal  action  ;  The  acid  ; 
Composite  sample  ;  Testing  skim  milk  ;  Sampling  frozen 
milk;  Cleaning  glassware;  Water  used  in  milk  testing; 
Care  of  test  bottles  and  apparatus 13 

CHAPTER  III 
MILK  FATS 

Composition  of  fats  ;  Kinds  of  butter  fats ;  Palmitin ;  Stearin  ; 
Olein ;  Butyrin  ;  Caproin  and  Caprylin ;  Glycerine  and 
fatty  acid  content  of  fats  ;  Food  value  of  fats  ;  Saponifi- 
cation  of  fats  ;  Iodine  absorption  of  butter  fats  ;  Volatile 
fatty  acids  of  butter  ;  Melting  point  and  physical  proper- 
ties of  butter 29 

vii 


CONTENTS 


CHAPTER  IV 

THE  LACTOMETER  AND  ITS  USE  IN  DETERMINING  MILK 
ADULTERATION 

PAGE 

Quevenne's  lactometer ;  Specific  gravity  of  milk  ;  Influence  of 
temperature  ;  Other  lactometers  ;  Influence  of  skimming 
and  watering ;  Calculation  of  solids  in  milk ;  Joint  use 
of  lactometer  and  Babcock  test  35 


CHAPTER   V 
MILK  SUGAR  AND  LACTIC  ACID 

Physical  properties  of  milk  kwgar ;  Fermentation  of  milk 
sugar  ;  Production  of  lactic  acid  in  the  milk ;  Determin- 
ing the  acidity  of  milk  ;  Calculating  the  acidity  of  milk  ; 
Alkaline  tablets ;  Acidity  of  cream 43 


CHAPTER  VI 
CREAM 

Composition  of  cream  ;  Testing  cream  ;  Methods  of  creaming ; 
Adulteration  of  cream  ;  Ripening  of  cream ;  The  use  of 
pure  cultures  ;  Influence  of  delay  on  the  creaming  of 
milk ;  Creaming  of  mixed  milks ;  Cream  raising  by 
dilution  .  50 


CHAPTER  VH 
THE  CHEMISTRY  OF  BUTTER  MAKING 

Churning ;  Dairy  salt ;  Buttermilk ;  Losses  of  fat  in  butter 
making ;  Composition  of  butter ;  Butter  colors ;  Over- 
runs j  Dividends  ;  Judging  butter 


CONTENTS  ix 

CHAPTER  VIII 
THE  SANITARY  CONDITION  OF  MILK 

PAGB 

Unwholesome  milk ;  Factors  influencing  the  sanitary  condi- 
tion of  milk  ;  Condition  of  the  animals  as  to  health ;  Care 
of  the  animals  ;  Care  of  milk  and  dairy  utensils ;  Food 
and  water  which  the  animals  receive ;  Colostrum  milk ; 
Tyrotoxicon ;  Fibrin  in  milk  ;  Gases  In  milk ;  Keeping 
qualities  of  milk  •  V  •  •  •  V  •  •  •  75 

CHAPTER  IX 
THE  CHEMISTRY  OF  CHEESE  MAKING 

Cheese  making  and  butter  making  compared ;  Proteids  in 
milk  ;  Case^in  ;  Albumin  ;  Rennet ;  The  rennet  test ; 
Process  of  cheddar  cheese  making ;  Process  of  stirred- 
curd  cheese  making;  Distribution  of  milk  solids  in  cheese 
making ;  Curing  of  cheese  ;  The  cheese  yield  of  milk ; 
Testing  cheese  by  the  Babcock  milk  test ;  Composition 
of  cheese  ;  Testing  whey  ;  Making  out  dividends  in  cheese 
factories;  Comparative  butter  and  cheese  returns  from 
milk ;  Different  kinds  of  cheese 88 

CHAPTER  X 
MILK  BY-PRODUCTS 

Uses  of  by-products;  Skim  milk  —  composition,  value,  and 
use  ;  Whey  —  composition,  value,  and  use  ;  Fertilizer 
value  of  milk  by-products ;  Comparative  value  of  skim 
milk  compared  with  milk  of  other  domestic  animals  .  107 

CHAPTER  XI 
THE  ADULTERATION  OF  DAIRY  PRODUCTS 

Oleomargarine  ;  Simple  methods  for  detecting  oleomargarine  ; 
Renovated  butter  ;  Adulteration  of  cheese  ;  Adulteration 
Of  milk  ;  Other  methods  for  testing  milk  ;  Dairy  laws  .  112 


X  CONTENTS 

CHAPTER  XII 
MARKET  MILK  AND  CREAM 

PAGE 

Variable  character  of  market  milk ;  Changes  in  composition 
of  milk  during  transportation ;  Pasteurizing  milk  and 
cream  ;  Condensed  milk ;  Milk  as  human  food  .  .  119 

CHAPTER  XIII 

INFLUENCE  OF  DIFFERENT  FOODS  UPON  THE  QUALITY 
OF  MILK  AND  DAIRY  PRODUCTS 

Food  and  milk  secretion ;  Feeding  fat ;  Production  of  hard 
butters  ;  Production  of  soft  butters  ;  Effects  of  individual 
foods ;  Desirable  flavors  in  milk  products ;  Influence  of 
balanced  rations  ;  Milk  secretion 125 

CHAPTER  XIV 

THE  RATIONAL  FEEDING  OF  DAIRY  STOCK 

I 

Uses  of  food  ;  Nutrients  and  their  functions ;  Dry  matter ;  x  / 
Ash  ;  Organic  matter ;  Proteids  ;  Carbohydrates  ;  Crude 
fiber ;  Crude  fat ;  Digestible  nutrients ;  Caloric  value  or 
heat  units  of  a  ration ;  Nutritive  ratio ;  Selection  of 
foods  for  rations  ;  How  to  calculate  a  ration  ;  Compara- 
tive cost  and  value  of  grains 131 

APPENDIX 

Tables  of  composition  of  fodders  and  feeding  stuffs  ;  Tables 
for  correction  of  lactometer  readings  ;  Review  questions  ; 
References .  147 

INDEX  .     187 


DAIRY  CHEMISTRY 


DAIRY   CHEMISTRY 


CHAPTER   I 

a  S  <?  <?  & 

THE  COMPOSITION  OF  MILK 

1.  Complexity   of    Composition.  —  When   milk   is 
separated  into  its  component  parts,  as  water,  fat, 
casein,  albumin,  sugar,  and  ash,  the  process  is  called 
analysis.     While  these  are  the  principal  compounds 
obtained  when  milk  is  analyzed,  there  are  a  num- 
ber of  other  substances  present  in  smaller  amounts 
which  affect  the  quality  of  milk  both  for  manufac- 
turing and  food  purposes.     Milk  is  one  of  the  vital 
fluids  of  the  animal  body  and  is  necessarily  of  com- 
plex composition. 

2.  Milk  Serum.  —  Of  the  various  constituents  of 
milk,  the  sugar,  ash,  and  albumin  are  in  solution, 
and  in  the  fresh  milk  the  casein  is  practically  in  a 
soluble  form.     The  fat,  however,  is  not  in  solution, 
but  is  in  the  form  of  minute  globules  suspended  in 
the  solution  which  contains  the  sugar,  ash,  albumin, 
and  casein  and  which  is  known  as  the  milk  serum. 
The  milk  serum  includes  all  of  the  constituents  of 
the  milk  except  the  fat.     The  term  "serum  solids" 
is  applied  to  those  substances  of  milk  which  are  dis- 
solved in  the  water,  —  the  sugar,  ash,  albumin,  and 
casein  taken  collectively. 

B  1 


2 


DAIRY  CHEMISTRY 


3.  Milk  Solids. —  When  milk  is  evaporated  to  dry- 
ness,  the  water  is  expelled  and  the  milk  solids  are 
obtained.  Milk  solids  are  a  mechanical  mixture  of 
fat,  casein,  albumin,  milk  sugar,  and  ash.  Normal 
milk  contains  about  13  per  cent  of  solid  matter  ;  some 
samples  contain  as  low  as  12  and  a  few  as  high  as 
14  per  cent.  The  amount  of  milk  solids  varies  pro- 
portionally with  the  fat  content  of  the  milk,  the  higher 
the  per  cent  of  fat  the  larger  the  amount  of  solids. 

In  the  chemical  analysis  of  milk,  the  solids  are 
obtained  by  evaporating  a  weighed  quantity  of  milk 
to  dryness  in  a  small  dish  which  has  previously  been 
carefully  weighed  on  a  very  delicate  balance.  The 
weight  of  the  milk  solids  is  then  obtained  and  the 
percentage  amounts  calculated. 


EXAMPLE 

Weight  of  milk  +  dish 
Weight  of  dish 
Weight  of  milk 

Weight  of  dish  +  solids 
Weight  of  dish 
Weight  of  milk  solids 

10.51 : 1.345  : :  100  :  x. 
1.345  x  100 


GRAMS 

23.360 
12.850 
10.510 

14.195 

12.850 

1.345 


=  12.80  per  cent  solids. 

100  - 12.80  =  87.20  per  cent  water. 
1     The   per   cent   of   water   in 

FIG.  1.  — Determining  the  solids 

in  milk.  milk  is  obtained  by  subtract- 


THE  COMPOSITION  OF  MILK  3 

ing  the  per  cent  of  solids  from  100,  as  the  loss  in 
weight  during  evaporation  is  the  water  expelled 
as  steam.  There  are  rarely  more  than  88  pounds  of 
water  in  100  pounds  of  milk ;  average  milk  contains 
about  87  per  cent,  while  some  of  the  richest  milks 
contain  86  per  cent  or  less.  The  milk  solids,  unless 
obtained  in  a  specially  constructed  water  oven,  are 
brown  in  color,  due  to  slight  charring  of  the  sugar 
and  other  compounds.  The  solids  of  milk  are  some- 
times termed  dry  matter  and  sometimes  solid  matter. 
They  are  composed  of  fat,  casein,  sugar,  albumin,  ash, 
and  other  compounds  found  in  smaller  amounts. 

4.  Milk  Fats.  —  Average  milk  contains  about  3.5 
per  cent  of  fat ;  some  normal  samples  may  contain 
3  per  cent  or  less,  while  others  may  contain  5  per 
cent  or  more.  Fat  is  the  most  variable  constitu- 
ent in  milk.  Cream  contains  ordinarily  from  18  to 
35  per  cent  of  fat,  and  well-made  butter  about  85  per 
cent.  For  butter-making  purposes  the  value  of  the 
milk  is  directly  proportional  to  its  fat  content.  Milk 
fat  is  mainly  familiar  as  the  product  obtained  by 
churning  cream.  Milk  fat  and  commercial  butter, 
however,  are  not  synonymous  terms.  By  milk  fat 
is  meant  the  pure  dry  fat,  free  from  water,  salt,  or 
casein,  while  butter  contains  all  of  these  materials 
in  variable  amounts.  The  determination  of  the  fat 
in  milk  by  the  Babcock  test  is  discussed  in  the 
second  chapter  of  this  work,  and  the  composition 
and  properties  of  the  fats  are  considered  in  other 
chapters. 


4  DAIRY  CHEMISTRY 

As  previously  stated,  the  fat  in  milk  is  not  present 
in  solution,  but  in  suspension  in  the  form  of  minute 
globules.  These  milk  fat  globules  are  about  one  five- 
thousandth  of  an  inch  in  diameter.  A  cubic  milli- 
meter of  milk  is  estimated  to  contain  from  2,000,000 
to  4,000,000  fat  globules,  or  a  single  drop  from 
100,000,000  to  150,000,000.  Under  the  microscope 
the  fat  globules  appear  grouped  together  in  small 
colonies.  The  size  of  the  fat  globules  varies  (1)  with 
the  breed  and  individuality  of  the  animal,  and  (2) 
according  to  the  length  of  time  the  animal  has  been 
in  milk.  When  a  cow  is  fresh,  there  is  a  smaller 
number  of  globules,  but  the  globules  are  larger  ; 
when  the  cow  is  well  along  in  her  milking  period,  the 
globules  are  smaller  but  more  numerous.  The  milk 
from  the  Channel  Island  breeds  is  characterized  by 
large  fat  globules,  while  the  milk  from  the  lowland 
breeds  contains  smaller  globules.  The  fat  globules 
must  be  massed  together  and  collected  when  butter 
is  made.  The  more  completely  they  are  recov- 
ered, the  greater  will  be  the  amount  of  butter 
produced. 

The  fat  globules  are  simply  solid  masses  of  fat. 
At  one  time  it  was  believed  that  they  were  sur- 
rounded by  a  membrane,  and  in  churning  it  was 
supposed  that  the  membrane  had  to  be  broken  before 
the  globules  would  mass.  Recent  chemical  investi- 
gations have  shown  that  there  is  no  membrane  sur- 
rounding the  fat  globules.  The  fat  globules  are 
lighter  than  any  of  the  constituents  of  the  milk 


PLATE   I 


JERSEY   MILK   FAT   GLOBULES 


PLATE   II 


HOLSTEIN    MILK   FAT   GLOBULES 


THE  COMPOSITION  OF  MILK  5 

8erum.  They  retain  their  form  and  individuality  on 
account  of  surface  tension,  which  is  the  pressure  that 
is  exerted  on  the  surface  of  the  globules  and  is  equal 
on  all  sides,  hence  the  spherical  form  of  the  globules. 

5.  Casein. — Average  milk  contains  about  3  per 
cent  of  casein,  which  in  fresh  milk  is  practically  in  a 
soluble  condition,  but  in  sour  milk  is  precipitated  as 
curd.     The  per  cent  of  casein  in  milk  is  quite  con- 
stant, ranging  from  2.8  to  3.5  per  cent.     As  a  general 
rule,  normal  milk  contains  less  casein  than  fat.     In 
a   pure    state    casein   is    a    grayish    white    powder. 
Casein  takes  a  very  important  part  in  cheese  making 
and  other  dairy  operations.     Its  chemical  and  physi- 
cal properties  and  the  changes  which  it  undergoes 
will  be  considered  in  other  chapters. 

6.  Albumin.  —  Average  milk   contains  about  one 
half  of  one  per  cent  of  albumin,  which  is  nearly  iden- 
tical with  egg  albumin,  or  the  "  white  "  of  the  egg. 
Albumin  and   casein   have  about   the  same  general 
composition,  but   different  properties  ;   they  belong 
to  the  class  of  bodies  called  proteids,  and  are  very 
complex  in  composition,  differing  from  fat  and  sugar 
by  containing   the  element   nitrogen,  which    is  not 
found  in  the  fats  and  sugars.     When  fresh  milk  is 
boiled,  the  coagulum  which  forms  on  the   surface  is 
albumin.     The  amount  of  albumin  in  milk  is  quite 
constant  and  ranges  from  one  half  to  three  quarters 
of  a  per  cent. 

7.  Milk  Sugar.  —  Lactose,  or  milk  sugar,  is  present 
in  milk  to  the  extent  of  about  5  per  cent.     When 


6  DAIRY  CHEMISTRY 

obtained  in  the  pure  state,  it  resembles  in  appearance 
confectionery  sugar,  but  not  in  taste.  Milk  sugar 
takes  an  important  part  indirectly  in  butter  and 
cheese  making,  as  it  is  the  material  from  which  the 
acid  is  formed  that  sours  the  milk.  The  amount  of 
milk  sugar  or  lactose  in  milk  is  quite  constant, 
ranging  from  4.6  to  5.4  per  cent.  In  average  milk 
it  is  the  constituent  which  is  present  in  the  larg- 
est amount  of  any  of  the  milk  solids.  The  part 
which  milk  sugar  takes  in  butter  and  cheese  mak- 
ing will  be  considered  in  other  chapters  of  this 
work. 

8.  Ash.  —  When  the  milk  solids  are  burned,  there 
is  a  small  amount  of  grayish  white  ash  obtained. 
The  ash  content  of  milk  is  constant  and  varies  but 
little  from  three  quarters  of  one  per  cent.  Milk  ash 
is  composed  of  common  salt,  and  phosphates  and 
chlorids  of  potassium,  calcium,  and  magnesium,  to- 
gether with  small  amounts  of  other  minerals.  A 
portion  of  the  phosphorus  is  in  combination  with  the 
casein. 

When  milk  is  analyzed  in  the  laboratory,  the  ash 
is  obtained  by  completely  burning  the  milk  solids  at 
a  low  temperature.  The  small  dish  containing  the 
milk  solids  (see  section  3)  is  placed  either  over  a 
specially  regulated  flame  or  in  a  low-temperature 
muffle  furnace  to  completely  burn  the  sugar,  casein, 
albumin,  and  fat  without  volatilizing  any  of  the 
mineral  salts.  The  dish  containing  the  milk  ash 
is  then  weighed  and  the  per  cent  of  ash  determined. 


THE  COMPOSITION  OF  MILK 


EXAMPLE 


Milk  taken  10.51   gm.     See 
section  3. 

GRAMS 

Dish  and  milk  ash        12.928 
Dish  12.850 

Ash  0.078 

10.51 :  .078  : :  100  :  x. 
.078  x  100 
10.51 


.74  per  cent  ash. 


9.  Variations  in  Com- 
position of  Milk.  —  Aver- 
age milk  has  about  the 

following    general    Com- 

.   . 

position  :  — 


FlG-  2.  —  Determining   the  ash  in 

milk. 


PER  CENT 

RANGE,  PER  CENT 

Water                  

87.00 

89.6  to  82.4 

Fat    

3.50 

2.5  to    6.0 

3.25 

2.5  to    4.0 

050 

0  5  to    0.8 

Milk  Sugar     

5.00 

4.3  to     6.0 

Ash                          

075 

0  6  to    0.8 

Solids 

13.00 

10.4        17.6 

It  is  seldom  that  the  extreme  limits  as  given  for  the 
composition  of  milk  are  met  with ;  occasionally  an 
individual  animal  may  give  milk  of  abnormally  high 
or  low  solids  and  fat,  but  it  is  rarely  the  case  that 
the  milk  from  an  entire  herd  will  contain  either  the 


DAIRY  CHEMISTRY 


maximum  or  the  minimum  percentage  of  milk 
solids. 

Milk  varies  in  composition  with  the  individuality 
of  the  animal,  period  of  lactation,  care,  exhaustive- 
ness  of  milking,  general  condition  as  to  health,  and 
nature  of  the  food  consumed.  Individuality,  as 
breed  characteristics,  influences  the  composition  of 
milk  to  a  greater  extent  than  the  other  factors 
enumerated.  The  extent  to  which  some  of  these 
factors  influence  the  composition  of  milk  will  be 
discussed  in  other  chapters  of  this  work. 

As  an  example  of  the  composition  of  milk  from 
different  breeds,  the  following  table  taken  from  the 
New  York  Experiment  Station,  and  representing 
one  year's  work,  is  given  :  — 


BREEDS 

TOTAL 
SoLins 
PER  CEXT 

FAT 

PER  CENT 

CASEIN 
PER  CENT 

MILK 
SUGAR 
PER  CENT 

ASH 
PER  CENT 

Holstein-Fresian 

12.39 

3.46 

3.39 

4.84 

0.74 

Ayrshire 

13.06 

3.57 

3.43 

5.33 

0.70 

Jersey 
Am.  Holderness 

15.40 
12.63 

5.61 
3.55 

3.91 
3.39 

5.15 
5.01 

0.74 
0.70 

Guernsey 
Devon 

14.60 
13.77 

5.12 
4.15 

3.61 
3.76 

5.11 
5.07 

0.75 
0.76 

While  these  figures  do  not  necessarily  hold  true  for 
all  herds,  or  for  individual  animals  of  any  breed, 
they  show  the  average  composition  of  the  milk  for 
an  entire  season  from  a  number  of  representative 
animals  of  different  breeds.  In  determining  the 


THE  COMPOSITION  OF  MILK 


value  of  milk  for  butter  or  cheese  making  purposes, 
the  yield  in  pounds  as  well  as  the  percentage  compo- 
sition of  the  milk  must  be  considered,  as  it  frequently 
happens  that  the  cows  giving  the  richest  milk  also 
give  the  smallest  yield  of  milk. 

10.  Percentage  Composition  and  Total  Yields.  —  In 
order  to  determine  the  total  yield  in  pounds  of  each 
constituent  produced  by  a  cow  or  by  a  herd  for  a 
given  period,  the  total  weight  of  milk  is  multiplied 
by  the  percentage  composition.  In  case  it  is  desired 
to  compare  the  yields  of  milk  solids  of  two  cows, 
giving  respectively  a  total  of  110  and  140  pounds  of 
milk  in  three  days,  an  analysis  would  have  to  be 
made  of  each  milk.  Suppose  the  milks  give  the 
following  results  upon  analysis  :  — 


COMPOSITION  OF  MILK 

Cow  No.  1 
PEE  CENT 

Cow  No.  2 
PER  CENT 

Milk  solids  

13.14 

12  56 

Milk  fats                         .     . 

4  06 

3  26 

Casein  and  albumin      

3.34 

3.54 

Ash     

0  70 

0  72 

5  04 

5"04 

TOTAL  YIELD  OF  MILK  SOLIDS 


Cow  No. : 

Milk  fats,  110  x  .0406  =  4.47 
Casein,  110  x. 0334=  3.67 
Ash,  110  x. 007  =  0.77 

Sugar,        110  x  .0504  =   5.54 
Total  •      14.45 


Cow  No.  2 

140  x. 0326=  4.56 

140  x. 0354=  4.95 

140  x. 0072=  1.01 

140  x. 0504=  7.06 


17.58 


10  DAIRY  CHEMISTRY 

While  the  difference  in  percentage  composition  of 
the  milk  is  .8  of  a  per  cent  of  fat  in  favor  of  cow 
No.  1,  the  total  yield  of  fat  for  three  days  is  .1  of 
9,  pound  in  favor  of  cow  No.  2.  Cow  No.  2,  how- 
ever, produced  a  larger  amount  of  milk  solids  in  the 
form  of  fat  than  cow  No.  1.  In  general  it  is  to 
be  noted  that  whenever  a  cow  produces  a  pound 
of  butter  fat,  she  also  produces  about  1.1  of  milk 
sugar,  about  a  pound  of  casein  and  albumin,  and 
about  .15  of  a  pound  of  ash.  When  milk  is  paid  for 
on  the  basis  of  its  fat  content  for  butter  making 
purposes,  the  total  pounds  of  fat  are  obtained  by 
multiplying  the  weight  of  the  milk  by  its  per  cent 
of  fat,  as  287  pounds  of  milk  testing  3.6  per  cent 
fat  contain  (287  x  .036)  10.33  pounds  of  fat.  In 
dairy  operations  all  comparisons  and  calculations 
are  made  on  the  basis  of  the  total  fat. 

11.  First  or  Fore  Milk  and  Strippings.  —  As  is 
well  known,  the  first  portion  of  milk  given  by  any 
cow  at  a  milking  is  poor  in  fat,  while  the  last 
portion,  or  strippings,  is  very  rich  in  fat.  The 
per  centage  amounts  of  casein,  ash,  and  sugar,  and 
other  ingredients,  however,  remain  nearly  constant. 
The  difference  in  fat  content  between  the  first  or 
fore  milk  and  the  strippings  suggests  the  impor- 
tance of  careful  and  exhaustive  milking,  and  also 
thorough  mixing  of  the  milk  before  taking  a  sample 
for  analysis.  The  composition  of  the  first  pint  and 
the  last  pint  of  milk  from  two  cows  is  given  as  an 
illustration. 


THE  COMPOSITION   OF  MILK 


11 


Cow 

No.  1 

Cow 

No.  2 

First  pint 

Last  pint 

First  pint 

Last  pint 

Total  solids  

per  cent 

942 

per  cent 

1949 

per  cent 

10  10 

per  cent 
1847 

Fat 

071 

10  84 

1  02 

9  49 

Solids,  not  fat    .... 
Ash 

8.71 
068 

8.65 
079 

9.08 
0  70 

8.98 
074 

Casein,  albumin     .     .     . 

3.44 

3.51 

3.35 

3.65 

12.    Milk  Serum,  Constancy  of   its  Composition.  — 

The  solids  of  the  milk  serum  are  fairly  constant  in 
composition.     This  is  well  illustrated  in  the  example 


MilK     Wer     Fat    Casein  /titK&prfl/JXffln    fish 

FIG.  3.  —  Average  composition  of  milk. 

given  of  the  composition  of  first  or  fore  milk  and 
strippings.  The  solids  of  the  milk  serum,  also 
known  as  the  solids  not  fat,  are  never  less  than  8.25 
per  cent  and  rarely  more  than  9.75  per  cent.  The 


12  DAIRY  CHEMISTRY 

average  is  about  9  per  cent.  The  greatest  difference 
in  the  composition  of  various  milks  is  in  the  fat  con- 
tent. Any  material  increase  in  the  total  solid  mat- 
ter of  milk  is  due  mainly  to  an  increase  of  the  fat. 
The  solids  not  fat  are  subject  to  but  slight  varia- 
tions compared  with  the  fluctuations  of  the  fat. 

Nearly  all  of  the  important  fluids  of  the  body,  like 
the  blood,  are  normally  quite  constant  in  chemical 
composition.  With  milk  the  constancy  of  composi- 
tion is  confined  mainly  to  the  serum  solids,  or  solids 
not  fat. 


CHAPTER  II 

MILK  TESTING 

13.  Importance  of  Milk  Testing.  —  A   knowledge 
of  the  fat  content  of  milk  is  essential  in  order  to 
determine  (1)  any  unnecessary  waste  in  the  manu- 
facture of  butter  and  cheese,  (2)  the  value  of  indi- 
vidual cows,  (3)  the  cost  of  producing  milk,  (4)  the 
value  of  different  fodders  and  grains  for  milk-pro- 
ducing purposes,  and  (5)  the  commercial  value  of 
milk. 

A  number  of  simple  methods  have  been  proposed 
for  testing  milk ;  some  of  them  require  a  more 
extended  knowledge  of  chemical  operations  than 
others.  The  method  which  is  in  most  general  use 
on  account  of  its  accuracy,  simplicity,  and  cheapness 
is  the  Babcock  centrifugal  method. 

14.  Reliability  of  the  Babcock  Test.  —  This  method 
has  been  tested  by  many  chemists,  and  in  all  cases 
it  has  been  found  to  give  reliable  results.     There  is 
a  tendency,  however,  to  read  the  fat  percentages  too 
low.     This  will  be  considered  more  in  detail  in  dis- 
cussing that  part  of  the  operation.     In  the  case  of 
skim  milk  and  buttermilk,  when  the  fat  is  present 
to  the  extent  of  only  two  tenths  of  a  per  cent  or  less, 
the  method  may  not  give  absolute  results.      This 

13 


14  DAIRY  CHEMISTRY 

does  not  impair  the  usefulness  of  the  test,  because 
frequently  the  losses  in  skim  milk  and  buttermilk 
are  greater  than  this,  and  so  far  as  the  whole  milk  is 
concerned  the  method  is  perfectly  reliable.  When 
the  Babcock  test  shows  only  a  trace  of  fat  in  the 
skim  milk  or  buttermilk,  the  losses  are  very  small. 

15.  Sampling  Milk.  —  Milk  should  be  thoroughly 
mixed  before  sampling.  The  milk  as  it  comes  from 
the  cow  or  when  it  has  been  standing  is  not  in  a 
condition  to  sample  until  it  has  been  thoroughly 
mixed,  either  by  pouring  from  one  pail  to  another 
or  by  stirring  with  a  long-handled  dipper.  Milk 
brought  to  the  creamery  in  cans  also  requires  thor- 
ough mixing  before  sampling.  This  is  best  accom- 
plished by  the  use  of  a  long-handled  dipper.  Before 
sampling,  the  milk  should  be  weighed. 

The  milk  should  not  be  measured  into  the  test 
bottles  when  it  is  either  hot  or  cold.  At  a  tigh 
temperature  the  milk  is  expanded  and  may  contain 
an  abnormal  amount  of  dissolved  air  ;  while  at  a  low 
temperature  the  milk  may  be  unduly  contracted.  A 
temperature  of  70°  to  80°  is  the  most  suitable  for 
measuring  milk.  If  the  milk  has  been  standing  for 
some  time  in  the  sample  bottle,  it  is  necessary  to  mix 
it  thoroughly  before  measuring  with  the  pipette. 
To  do  this,  turn  the  milk  from  the  sample  bottle  into 
another  bottle  or  dish,  pouring  it  down  the  side  to 
prevent  the  formation  of  foam.  In  case  the  sample 
bottle  has  been  standing  until  the  fat  has  separated 
into  a  layer  of  cream,  the  bottle  may  be  placed  in  a 


MILK   TESTING 


15 


bath  of  warm  water,  temperature  100°,  to  liquefy  the 
fat  before  mixing.  Milk 
which  shows  the  pres- 
ence of  clots  of  cream  or 
small  particles  of  butter 
formed  during  the  shak- 
ing of  the  sample  bottle 
is  not  in  condition  to 
be  measured  with  the 
pipette.  If  the  sam- 
pling of  the  milk  has  not 
been  carefully  done,  the 
work  of  testing  is  of  little 
value,  as  the  sample 
taken  fails  to  represent 
the  milk  tested. 

16.  Measuring  Milk 
with  the  Pipette.  —  The 
apparatus  used  for  meas- 
uring the  milk  is  called 
a  pipette  (see  Fig.  4).  In 
order  to  fill  the  pipette 
put  the  pointed  end  into 
the  milk,  apply  suction 
with  the  mouth  until 
the  milk  rises  just  above 

the  point  a  on  the  stem  ; 

.          ,.  -.       .,,       FIG.  4.  — Measuring  milk  with  the 

then  close  the  end  with  pipette. 

the  index  finger  of  the 

right  hand,  holding  the  pipette  in  the  way  shown 


16  DAIRY  CHEMISTRY 

in  the  cut.  The  second  and  third  fingers  are  opposite 
the  thumb,  while  the  little  finger  rests  against  the 
stem.  When  held  in  this  way,  the  pipette  is  pre- 
vented by  the  little  finger  from  swaying  sidewise  ; 
while  the  thumb,  with  the  second  and  third  fingers 
on  the  opposite  sides,  secures  a  good  hold  and  leaves 
the  index  finger  free  to  properly  control  the  flow  of 
milk  from  the  pipette,  and  thus  rapid  measurements 
can  be  made.  If  the  pipette  is  wet,  rinse  it  with  a 
little  of  the  milk  before  using  it.  In  passing  from  one 
milk  to  another,  clean  the  pipette  by  rinsing  it  with 
the  milk  that  is  to  be  tested.  The  pipette  should  be 
thoroughly  cleaned,  first  with  cold  water,  then  with 
hot  water  at  the  close  of  the  work.  The  pipette 
holds  17.6  cc.  of  water,  and  delivers  18  gm.  of 
milk.  Hold  the  test  bottle  in  the  left  hand  at  an 
angle  of  about  60°.  Let  the  tip  of  the  pipette  if 
large  just  touch  the  inside  of  the  neck  of  the  test 
bottle,  in  order  to  permit  air  to  pass  out  of  the  test 
bottle,  otherwise  the  milk  will  spatter.  Allow  plenty 
of  time  for  the  pipette  to  drain;  remove  the  last  few 
drops  by  blowing. 

17.  Making  the  Test.— The  test  bottle  (see  Fig. 
5)  is  provided  with  a  neck  which  has  a  graduated 
scale  from  1  to  10.  Each  larger  division  is  divided 
into  five  smaller  divisions,  each  representing  .2  of  a 
per  cent  of  fat.  The  test  bottle  is  usually  provided 
with  a  copper  collar  bearing  a  number.  Fill  the 
acid  measure,  Fig.  6,  up  to  the  17.6  cc.  mark  with 
sulphuric  acid.  The  action  of  the  sulphuric  acid 


MILK  TESTING 


17 


will  be  considered  in  another  paragraph.  Pour  the 
sulphuric  acid  from  the  acid  measure  into  the  test  bot- 
tle which  contains  the  milk.  The  acid  and  the  milk 
should  be  of  nearly 
the  same  tempera- 
ture, 70°  F. 

While  the  acid 
is  poured  in,  ro- 
tate the  test  bot- 
tle so  as  to  wash 
all  of  the  milk 
down  from  the 
stem.  After  the 
acid  is  added,  take 
the  bottle  by  the 
stem  and  mix 
the  acid  and  the 
milk  by  rotating. 
The  solution  be- 
comes a  dark  cof- 
fee color,  due  to 
FIG. 5. -Milk  test  the  acid  charring 

bottle.  °     FIG.  6.  —  Acid  measure, 

the  sugar.      The 

acid  first  precipitates  the  casein  and  then  dissolves 
it.     The  acid  does  not  act  on  the  fat. 

The  fat  is  separated  from  the  milk  serum  by  cen- 
trifugal action.  There  are  a  number  of  different 
kinds  and  sizes  of  centrifugal  machines,  but  they  all 
act  on  the  same  principle.  The  test  bottles  are 
placed  in  the  pockets  of  the  centrifugal  machine. 


18  DAIRY  CHEMISTRY 

In  case  there  are  not  enough  bottles  to  fill  the 
machine,  arrange  the  bottles  so  there  will  be  an 
even  number  on  each  side.  If  this  is  not  done, 
the  machine  is  unbalanced,  and  the  bearings  will 
soon  become  badly  worn.  The  bottles  are  to  be 
whirled  five  minutes  at  the  rate  of  900  revolutions 
per  minute.  Directions  for  speeding  the  machine 
will  be  found  in  another  paragraph.  The  start- 
ing and  stopping  of  the  machine  should  be  done 
gradually. 

After  whirling  five  minutes,  the  test  bottles  are  to 
be  filled  with  hot  water  up  to  about  the  eighth  mark 
on  the  stem.  The  air  bubbles  which  are  sometimes 
caught  in  the  neck  should  be  allowed  to  escape.  The 
bottles  are  then  whirled  two  minutes  longer  in  order 
to  collect  all  of  the  fat  in  the  graduated  stem.  In 
using  the  machine  always  put  on  the  cover  so  as  to 
prevent  any  accident. 

None  of  the  apparatus  used  in  this  test  is  patented, 
and  a  good  homemade  centrifugal  machine  will  answer 
every  purpose.  The  bottles  and  other  glassware  can 
be  purchased  separately. 

18.  Reading  the  Fat.  —  When  the  test  is  completed, 
the  fat  in  the  stem  of  the  test  bottle  presents  the 
appearance  shown  in  Fig.  7.  Read  from  the  low- 
est point  b  to  the  highest  point  a.  Each  large  divi- 
sion, as  1  to  2,  represents  a  whole  per  cent  of  fat ; 
each  of  the  smaller  divisions  one  fifth  or  two  tenths 
of  a  per  cent.  Suppose  the  top  registers  seven  large 
divisions,  and  three  small,  then  a  =7.6.  If  b  registers 


MILK   TESTING 


19 


two  large  and  three  small  divisions,  b  =  2.6.     7.6  — 
2.6  =  5.0,  the  per  cent  of  fat  in  the  milk. 

Do  not  read  from  other  points  than  a  and  6,  other- 
wise the  results  will  be  too  low.  The  bottles  are 
made  to  read  in 
just  this  way. 
The  reading 
should  be  done 
before  the  fat 
cools  and  streaks 
down  the  sides. 
In  case  a  num- 
ber of  readings 
are  to  be  made, 
the  test  bottles 
should  be  set  in 
a  pan  of  hot 
water,  or  hot 
water  can  be 
run  into  the  pan 
of  the  machine, 
to  prevent  the 
bottles  from 
cooling.  Dividers  can  be  used  as  indicated  in  the 
figure,  but  should  be  spread  from  0  to  5. 

19.  Calibration  of  Test  Bottles.  —  All  test  bottles 
should  be  rejected  when  inaccuracy  of  the  divisions 
can  be  detected  with  the  eye.  In  the  most  careful 
work  they  should  be  calibrated  with  mercury:  27.18 
gm.  of  clean  metallic  mercury  should  just  fill  the 


FIG.  7.  — Reading  the  test. 


20  DAIRY  CHEMISTRY 

space  between  the  0  and  the  10  in  the  scale.  Each 
small  division  is  equal  to  .04  cc.,  or,  as  usually  made, 
about  one  and  one  half  millimeters.  The  test  bottles 
can  also  be  calibrated  with  water  in  the  following 
way:  The  bottles  are  filled  with  pure  distilled  water 
up  to  the  0  mark,  and  then  from  an  accurately 
graduated  burette,  graduated  to  ^  cc.,  water  is 
added.  It  should  require  2  cc.  of  water  to  fill  the 
test  bottle  from  the  0  to  the  10  mark.  For  ordinary 
work  the  bottles  can  all  be  tested  with  one  sample 
of  milk,  and  all  bottles  rejected  that  show  a  greater 
difference  than  one  small  division.  Accurately  gradu- 
ated test  bottles  can  usually  be  obtained  from  supply 
houses  that  deal  in  chemical  apparatus.  Inaccu- 
rately graduated  test  bottles  are  occasionally  the 
cause  of  much  trouble  and  dissatisfaction  in  the 
creamery. 

20.    Speeding  the  Machine.  —  A  centrifugal  of  14 
inches'  diameter  should  make  about  900  revolutions 


FIG.  8.  —  Centrifugal  machine. 

per  minute.     In  order  to  speed  the  machine  count 
the  number  of  revolutions  that  the  test  bottles  make 


MILK  TESTING  21 

for  every  revolution  of  the  crank  wheel.  Suppose 
the  test  bottles  make  12  revolutions  while  the  crank 
makes  one.  In  order  that  the  bottles  may  make  900 
revolutions  per  minute,  the  crank  must  be  turned 
75  times  in  a  minute  (900  -=-  12  =  75).  In  case  the 
machine  is  less  than  14  inches  in  diameter  a  greater 
number  of  revolutions  is  necessary. 

DIAMETER  OF  CENTRIFUGAL.    INCHES      NUMBEK  OF  REVOLUTIONS  PEE  MINUTB 
10  1050 

12  975 

14  900 

16  850 

18  800 

20  750 

21.  Centrifugal  Action.  —  As  previously  stated,  the 
fats  are  lighter  than  the  milk  serum,  and  when  the 
milk  is  whirled  in  the  test  bottles,  there  is  a  separation 
of  milk  fats  (lighter  particles)  from  the  milk  serum 
(heavier  portion).  The  serum  goes  to  the  outside 
of  the  circle  of  revolution,  while  the  fats  mass  in  the 
center,  where  they  are  finally  collected  in  the  gradu- 
ated stem  of  the  test  bottle.  The  sulphuric  acid, 
which  is  one  and  eight  tenths  heavier  than  water, 
also  aids  in  the  separation  both  by  increasing  the 
specific  gravity  of  the  milk  serum  and  by  chemical 
action  upon  the  albumin  and  casein.  The  cream 
separator  works  on  this  same  principle.  In  the  case 
of  the  separator,  provision  is  made  for  the  escape  of 
the  fat  into  a  tube  as  it  collects  at  the  center.  Cen- 
trifugal action  is  well  illustrated  by  whirlpools,  where 


22  DAIRY  CHEMISTRY 

all  of  the  foam  and  light  material,  as  leaves,  collect 
in  the  center. 

22.  The  Acid.  —  Commercial  sulphuric  acid  (sp. 
gr.  1.82),  about  90  per  cent  strength,  is  used. 
One  pound  of  acid  will  make  about  twenty  tests. 
When  the  acid  is  too  strong,  the  fat  presents  a 
blackened  and  charred  appearance ;  if  too  weak,  par- 
ticles of  undissolved  casein  appear  immediately 
below  the  fat  line.  When  just  right,  the  fat  sepa- 
rates in  a  distinct  and  well-defined  layer  and  looks 
like  butter.  If  the  acid  is  too  strong,  and  chars  the 
fat,  use  a  smaller  amount  in  making  the  test.  In 
that  case,  if  the  test  is  not  satisfactory,  the  acid 
should  be  exchanged  for  a  new  lot.  Do  not  attempt 
to  dilute  the  acid  with  water.  If  the  acid  is  too 
weak,  a  larger  amount  than  17.6  cc.  may  give  satis- 
factory results.  The  strength  of  the  acid  can  be 
determined  by  using  a  hydrometer  for  heavy  liquids, 
and  noting  the  depth  to  which  the  spindle  sinks  in 
the  acid.  To  obtain  the  best  results,  the  acid  should 
vary  but  little  from  1.82  specific  gravity  or  90  per 
cent  strength. 

STRENGTH  OF  Aon>  SPECIFIC  GRAVITY 

88  1.808 

89  1.815 

90  1.820 

91  1.825 

92  1.830 

93  1.834 

94  1.837 

95  1.839 


MILE  TESTING 


23 


The  acid  as  well  as  the  washings  and  contents  of  the 
test  bottles  can  be  handled  only  in  glass  or  earthen- 
ware. 

The  acid  should  never  come  in  contact  with  tin 
or  a  metallic  dish  of 
any  kind.  If  acid  is 
spilled  on  the  floor  or 
desks,  wash  it  up  imme- 
diately, using  plenty 
of  water.  If  a  large 
quantity  is  spilled,  ab- 
sorb it  with  sawdust, 
bran,  or  fine  clay.  In 
case  any  is  spilled  on 
the  clothing,  rinse  with 
water  and  then  apply 
ammonia  to  the  spots. 
Never  throw  the  acid 
waste  near  a  tree  or 
where  a  person  or  ani- 
mal is  obliged  to  walk. 

A  convenient  form 
of  apparatus  for  meas- 
uring the  acid  where  a 
large  number  of  tests 
are  to  be  made  is  shown 
in  Fig.  9.  a  is  the  , 

0  FIG.  9.  —  Acid  measuring  apparatus. 

acid   bottle  connected 

with  glass  tube  bb  to  a  pipette.     The  stopcock /can 

be  turned  so  as  to  allow  the  acid  to  run  into  the  test 


24  DAIRY  CHEMISTRY 

bottle  g.  The  automatic  pipette  is  fastened  to  an 
iron  stand  dd,  which  rests  upon  the  table.  Other 
forms  of  apparatus  are  also  in  use.  In  ordinary 
practice  a  strong  glass  vessel  with  a  good  lip  for 
pouring  is  the  most  satisfactory  arrangement  for 
handling  the  acid.  A  white  tile  is  excellent  to  have 
on  the  table  under  the  acid  bottle. 

23.  Composite  Sample.  — In  actual  creamery  prac- 
tice the  daily  testing  of  each  patron's  milk,  or  in  the 
dairy,  the  testing  of  both  morning's  and  evening's 
milk  from  each  cow  is  too  expensive.  To  obviate 
this  daily  testing,  a  composite  or  compound  sample 
is  made  up  by  saving  a  small  sample  of  each  milk  in 
a  pint  fruit  can.  At  the  end  of  one  week  or  of  two 
weeks  the  compound  sample  is  carefully  mixed  and 
tested.  Inasmuch  as  this  test  represents  a  propor- 
tional part  of  each  lot  of  milk,  it  gives  the  average 
amount  of  fat  in  the  milk  for  the  period.  In  cream- 
eries and  factories,  where  milk  is  paid  for  by  test, 
the  composite  test  when  properly  carried  out  gives 
good  results. 

The  composite  sample  should  be  kept  covered  so 
that  the  surface  of  the  cream  will  not  become  dry 
and  leathery.  The  sample  should  also  be  kept  in  a 
cool  place  to  prevent  fermentation. 

Various  chemicals  are  used  to  keep  the  milk  fresh. 
Potassium  bichromate  has  been  found  to  give  the 
best  satisfaction.  About  one  half  gram  of  potassium 
bichromate  will  be  sufficient  to  preserve  a  pint  of 
milk.  Winton  and  Ogden  state  that  a  .22  pistol 


MILK  TESTING  25 

shell  cut  one-half  inch  long  will  hold,  loosely  filled, 
approximately  one-half  gram  of  bichromate.  For 
convenience  in  handling  the  shell  can  be  soldered  to  a 
piece  of  stout  wire.  Put  the  bichromate  in  the  sam- 
ple cans  when  empty,  and  no  more  need  be  added  until 
a  new  composite  sample  is  started.  The  bichromate 
imparts  its  characteristic  yellow  color  to  the  milk. 

In  case  corrosive  sublimate  or  any  other  poisonous 
material  is  used  for  preserving  the  composite  sample, 
it  is  best  to  color  the  milk  with  aniline  so  as  to  pre- 
vent accidental  poisoning  from  use  of  the  milk. 

Small  four  or  six  ounce,  wide-mouthed  bottles  may 
be  used  for  holding  the  composite  samples.  Bottles 
with  glass  stoppers  are  the  best.  Rubber  stoppers 
may  be  used,  but  cork  stoppers  should  never  be  used. 
They  are  difficult  to  clean,  and  they  cause  the  milk  to 
sour.  When  the  composite  sample  becomes  "lumpy" 
and  is  difficult  to  sample,  a  very  small  (.1  gm.)  piece 
of  caustic  potash  may  be  added  before  mixing  the  milk. 
The  potash  will  dissolve  the  lumps  of  curd.  A  few 
drops  more  than  17.6  cc.  of  acid  should  then  be  used. 

When  only  a  small  number  of,  tests  are  to  be  made, 
the  following  plan  may  be  followed :  Save  about  two 
ounces  of  each  milk  separately  in  glass  bottles  or 
cans ;  at  the  next  milking  add  a  proportional  quan- 
tity. A  composite  sample  of  the  day's  milk  is  thus 
obtained,  and  while  still  fresh  is  mixed,  and  then  by 
means  of  a  small  pipette,  5.9  cc.  are  measured  into  a 
test  bottle  twice  the  size  of  those  ordinarily  used,  or 
test  bottles  made  for  35  cc.  of  milk.  In  a  similar 


26 


DAIRY  CHEMISTRY 


way  the  milk  for  six  days  may  thus  be  measured 
directly  into  the  test  bottles,  arid  then  tested. 

24.  Testing  Skim  Milk.  —  In  testing  skim  milk  the 
special  test  bottle  devised  by  Farrington,  with  the 

small  neck  and  the  side  tube  for 
the  addition  of  the  acid,  should 
be  used  (see  Fig.  10).  Each 
division  on  the  neck  represents 
.05  of  a  per  cent.  In  using  these 
bottles,  it  must  be  remembered 
that  the  small  amount  of  fat  ob- 
tained in  the  neck  is  not  neces- 
sarily all  of  the  fat  in  the  skim 
milk,  because  some  of  it  may  be 
present  in  such  a  fine  state  of  divi- 
sion that  it  is  not  brought  up  into 
the  neck.  Hence  the  results  are 
usually  slightly  lower  than  those 
obtained  by  chemical  analysis. 
This,  however,  does  not  seriously 
impair  the  test.  When  the  test 
shows  only  a  trace  of  fat,  the 
FIG.  io.-Skim  milk  test  butter  maker  can  feel  satisfied  that 
he  is  doing  good  work. 

25.  Sampling  Frozen  Milk.  —  When  a  can  of  milk 
freezes,  the  ice  forms  on  the   outside  and  there  is 
usually  a  central  part  that  does  not  freeze.     The  un- 
frozen part  is  richer  in  fat  and  solids  than  the  frozen 
part.     The  ice  in  the  center  of  a  can  is  richer  in  milk 
solids  than  the  ice  of   the  outer  portions.      When 


MILK  TESTING  27 

frozen  or  partially  frozen,  milk  is  not  in  a  condition 
to  sample,  but  should  be  allowed  to  thaw  and  then  be 
thoroughly  mixed. 

26.  Cleaning  Glassware.  —  In  order  to  secure  the 
best  results,  the  test  bottles  and  all  of  the  glassware 
used  in  testing  milk  should  be  kept  clean.     The  test 
bottles  should   be  emptied   before  the   fat   becomes 
cold  and  hard.     By  shaking  the  test  bottle,  the  sedi- 
ment of  lime  sulphate  or  gypsum  is  removed   with 
the  acid  mixture.     The  test  bottles  can  be  left  to 
drain  on  the  drain  board  placed  over  the  acid  waste 
jar.     A  drain  board  with  holes  large  enough  to  receive 
the  neck  of  the  test  bottle  will  be  found  very  useful 
in  handling  a  large  number  of  test  bottles.     The  test 
bottles  should  be  rinsed  while  still  hot  with  warm 
water  and  after  draining  this  should  be  followed  by 
a  second  rinsing  with  hot  water.     A  small  brush  will 
be  found  useful  in  keeping  the  necks  of  the  bottles 
clean.     Occasionally  it  will  be  necessary  to  give  the 
test  bottles  a  bath  in  hot  water  containing  a  little 
alkali,  sal  soda,  Babbitt's  potash,  gold  dust,  or  any 
similar   material   dissolved   in    the   water   in   small 
amounts.     A  small  copper  tank  large  enough  to  re- 
ceive a  rack  containing  twelve  to  twenty-four  test 
bottles  so  they  may  be  completely  immersed  will  en- 
able the  creamery  or  factory  man  to  keep  his  test 
bottles  in  a  good  condition. 

27.  Water  used  in   Milk   Testing.  —  Hard  waters 
containing  large  amounts  of  lime  or   alkaline  salts 
are  not  suitable  for  use  in  milk  testing.     Rain  water 


28  DAIRY  CHEMISTRY 

or  other  soft  water  or  condensed  steam  is  preferable. 
When  water  containing  lime  is  used,  bubbles  of  gas 
are  given  off,  causing  foam  when  the  hot  water  is 
added  to  the  test  bottles  containing  the  acid.  The 
presence  of  foam  in  the  graduated  stem  of  the  test 
bottle  prevents  accurate  reading  of  the  fat.  Some 
hard  waters  are  suitable  for  use  provided  a  few  drops 
of  sulphuric  acid  are  added  before  heating.  If  this 
is  done,  of  course  the  water  cannot  be  heated  or  used 
in  ordinary  metal  boilers  and  receptacles.  When  a 
large  number  of  tests  are  to  be  made,  a  suitable  out- 
fit should  be  provided  for  the  addition  of  hot  water 
to  the  test  bottles  ;  a  pail  suspended  three  or  four 
feet  above  the  tester  with  a  rubber  tube,  a  pinch 
cock,  and  a  glass  tube  drawn  to  a  point,  will  be  found 
suitable  for  this  purpose. 

28.  Care  of  Test  Bottles  and  Apparatus. — The 
rims  on  the  necks  of  test  bottles  are  easily  nicked 
and  broken,  and  in  handling  bottles,  care  should  be 
exercised  to  prevent  this  being  done.  Some  bottles 
are  provided  with  ground  or  roughened  places  for 
labeling  or  marking  with  pencil,  while  others  have 
numbered  copper  or  metal  "  collars."  In  making  the 
test,  the  numbers  should  be  carefully  checked,  and 
the  proper  entries  made  as  to  the  sample  and  the  fat 
content.  Many  conveniences  in  the  way  of  home- 
made racks  and  devices  for  holding  the  apparatus 
will  suggest  themselves.  In  milk  testing,  cleanliness 
and  accuracy  in  all  the  manipulations  are  the  main 
essentials  for  securing  correct  results. 


CHAPTER  III 

MILK  FATS 

29.  Composition    of    Fats.  —  The  fat  globules   of 
milk  are  a  mechanical  mixture  of  several   separate 
fats.     All  fats  are  composed  of  the  elements  carbon, 
hydrogen,  and  oxygen ;  but  individual  fats  differ  in 
the  way  in  which  these  elements  are  combined.     In 
all  the  fats,  carbon,  the  principal  element  found  in 
coal,  is  present  to  the  extent  of  over  75  per  cent.     The 
fats  as  a  class  do  not  contain  any  nitrogen,  differing 
in  this  respect  from  casein  and  albumin,  which  con- 
tain about  16  per  cent  of  this  element.     Each  fat  has 
its    own    melting   point,    form    of    crystals,  specific 
gravity,    and   other  characteristics,   and   hence    the 
physical  properties  of  butter  are  largely  dependent 
upon  the  proportion  in  which  the  principal  fats  are 
present.     Some  of  the  milk  fats  are  hard,  and  have  a 
high  melting  point,  while    others  are  liquid.      The 
character  of  butter,  as  hard  or   soft,   is  dependent 
largely  upon   the   proportion  in  which  the  various 
fats,  as  stearin,  palmitin,  and  olein,  are  present. 

30.  Kinds  of  Butter  Fats.  —  The  various  fats  which 
are  present  in  butter  are  butyrin,  caproin,  caprylin, 
laurin,  palmitin,    myristin,  stearin,  and   olein.     Of 

29 


30  DAIRY  CHEMISTRY 

these  fats,  palmitin,  stearin,  and  myristin  make  up 
about  50  per  cent  of  the  composition  of  butter  fat, 
olein  about  38  per  cent,  and  butyrin,  the  character- 
istic fat  of  butter,  about  6  per  cent ;  the  remaining 
6  per  cent  being  made  up  of  laurin,  capin,  caproin,  and 
caprylin.  For  practical  purposes,  butter  fats  may  be 
divided  into  three  classes  :  (1)  hard  fats,  stearin, 
palmitin,  and  myristin,  (2)  soft  fat,  olein,  (3)  charac- 
teristic fat,  butyrin. 

31.  Palmitin  is  a  white,  solid  fat  found  in  butter, 
and  also  obtained  from  palm  oil.     Human  fat  is  rich 
in  palmitin.     When  chemically  pure,  it  is  tasteless. 
Palmitin  forms  crystals  like  snowflakes.      This   fat 
has  a  high  melting  point,  145.4°  F. 

32.  Stearin  is  a  white,  solid  fat  like  palmitin,  and 
has  a  high  melting  point,  157°  F.     It  also  crystallizes 
in  the  same  way  as  palmitin.     For  a  long  time  these 
two  fats,  palmitin  and  stearin,  were  thought  to  be 
one   fat,  to  which  was   given  the  name  margarine. 
Among  the  fats  that  are  particularly  rich  in  stearin 
are  beef  and  mutton  tallow.     These  melt  at  a  much 
higher  point  than  butter,  and  are  the  materials  used 
in  the  adulteration  of  butter,  forming  a  large  part  of 
the   product   known   as  oleomargarine,  which   is   a 
mechanical  mixture  of  the  fats  palmitin  and  stearin 
(margarine)  with  olein.     The  larger  the  proportion 
of  either  stearin  or  palmitin  in  any  fat,  the  higher 
its  melting   point.     When  one  butter  has  a  higher 
melting  point  than  another,  it  is  due  to  the  presence 
of  a  larger  amount  of  palmitin  or  stearin.     These 


MILE  FATS  31 

two  fats,  with  myristin,  make  up  about  half  of  the 
Aveight  of  the  milk  fats. 

33.  Olein  is  quite  different  from  either  palmitin 
or  stearin.     This  fat  makes  up  about  40  per  cent 
of  the  weight  of  butter.    Under  ordinary  conditions 
olein   is  a   liquid.      It    solidifies   at   a   temperature 
of  40°  F.     It  is  liquid  at  the  ordinary  temperature 
of  the  cold   deep  setting  of  milk,  that  is,  the  set- 
ting of  milk  in  ice  water.     Olein  has  the  property 
of   readily   and  copiously  dissolving    palmitin    and 
stearin.     The  larger  the  per  cent  of  olein  in  a  butter 
or  fat,  the  softer  it  is.     Sperm  oil,  cod  liver  oil,  and 
many  of  the  vegetable  oils  are  rich  in  olein. 

34.  Butyrin   melts   at    a    temperature   of   77°  F. 
Milk  fats  contain  from  5  to  7  per  cent   of  buty- 
rin.     Although  it  forms  such  a  small  proportion  of 
milk  fat,  it  is  the  characteristic  fat  of  butter.     It  is 
the  butyrin  which  gives  to  butter,  its  individuality, 
and   its   presence  or   absence  is   the   distinguishing 
point  between  butter  and  oleomargarine.     Butyrin, 
when  decomposed,  forms   butyric  acid.     In  rancid 
and  stale  butter,  the  rank  odor  is  due  to  butyric 
acid.     Butyrin   is  not  as  stable  a   fat  as   palmitin, 
stearin,  or   olein. 

35.  Caproin  and  Caprylin  comprise  only  a  small 
part  of  the  fats  of  milk,  and  they  do  not  require  any 
special  consideration. 

36.  Glycerine  and  Fatty  Acid  Content  of  Fats.  — 
When  fats   are   broken   up   into   simpler   products, 
glycerine  is  one  of  the  substances  formed  ;  the  other 


32  DAIRY  CHEMISTRY 

product  is  a  fatty  acid  with  an  "  ic  "  ending  in  place 
of  the  "  in  "  ending  of  the  fat. 

By  the  action  of  superheated  steam, 

Palmitin  yields  palmitic  acid  and  glycerine. 
Olein  yields  oleic  acid  and  glycerine. 
Stearin  yields  stearic  acid  and  glycerine. 
Butyrin  yields  butyric  acid  and  glycerine. 
Caproin  yields  caproic  acid  and  glycerine. 
Caprylin  yields  caprylic  acid  and  glycerine. 

Glycerine  is  alkaline  in  its  properties,  and  it  is  the 
glycerol  radical  which  unites  with  the  fatty  acids 
to  form  neutral  fats.  Milk  fats  are  frequently 
denned  as  glyce rides  of  the  fatty  acids.  They  are 
neutral  bodies.  All  of  the  fats  are  lighter  than 
water.  The  mixed  butter  fats  are  insoluble  in 
water  ;  all  are  soluble  in  ether,  chloroform,  gasoline, 
and  similar  solvents.  Butyrin,  caproin,  and  capry- 
lin,  when  exposed  to  air  and  light  for  any  length  of 
time,  undergo  decided  changes  in  composition,  which 
finally  result  in  the  production  of  the  corresponding 
fatty  acids  which  are  present  in  rancid  butter. 

37.  Food  Value  of  Fats.  —  Fat  is  a  concentrated 
form  of  heat-producing  food,  because  it  contains 
such  a  large  amount  of  carbon.  In  very  small  seeds, 
like  flax,  the  fat  is  one  of  the  main  reserve  forms  of 
food.  One  pound  of  fat  when  burned  will  produce 
about  two  and  one  fourth  times  more  heat  than  a 
pound  of  starch.  Butter,  which  contains  about  85 
per  cent  of  fat,  is  valuable  in  a  ration  for  the  heat 
and  energy  which  it  produces. 


MILK  FATS  33 

38.  Saponification  of  Fats.  — When  certain  chemi- 
cals, known  as  alkalies,  such  as  potash  and  soda,  are 
heated  with   fat,  they  form  soap  ;    the   process   is 
called    saponification.       When    saponification    takes 
place,  part  of  the  alkali  unites  with  the  fatty  acid 
of  the  fat  and  forms  soap,  while  the  glycerine  radical 
of  the  fat  unites  with  the  remainder  of  the  alkali 
and  forms  glycerine. 

39.  Iodine  Absorption  of  Butter  Fats.  —  In  common 
with  other  fats,  butter  fats   have    the   property  of 
absorbing  a  definite  amount  of  iodine.     The  iodine 
number  of   butter,  or  the  percentage  of  iodine  ab- 
sorbed by  the  fats,  ranges  from  28  to  35,  while  lard, 
tallow,   cotton-seed   oil,  and  other   commercial  fats 
and  oils  generally,  have  a  greater  capacity  to  absorb 
iodine  and  hence  have  a  higher  iodine  absorption 
number.      The   iodine    absorption     number    is   fre- 
quently used   as   an   aid   in    detecting    adulterated 
samples  of  butter. 

40.  Volatile  Fatty  Acids  of  Butter.  —  When  butter 
fats  are  saponified  and  free  fatty  acids  are  liberated, 
about  8  per  cent  of  the  volatile  fatty  acids  are  also 
liberated  and  are  volatilized  in  a  current  of  steam. 
In  the   analysis  of   butter,  the  amount  of  volatile 
fatty   acids  obtained   from   5   gm.  usually  requires 
from    27    to    28    cc.    of    a    tenth    normal    solution 
of  alkali  for  neutralization  ;    this  is  known  as  the 
Reichert-Meissel  value  of  butter,  and  is  extensively 
used  in  detecting  adulterated  butter.     Spurious  sam- 
ples, as  oleomargarine   and   butterine,  have  a   low 


34  DAIRY  CHEMISTRY 

value,  less  than  3,  because  of  their  not  containing 
any  butyric  acid. 

41.  Melting  Point  and  Physical  Properties  of 
Butter.  —  Normal  butter  has  a  melting  point  of 
about  33°  C.  Butter  with  an  abnormal  melting 
point  is  of  poor  quality  because  of  an  excess  of 
some  fat,  as  olein,  stearin,  or  palmitin.  The  specific 
gravity  of  butter  fat  ranges  from  .867  to  .87  when 
taken  at  a  temperature  of  100°  C.  and  compared  with 
water  at  15°  C.,  or  when  compared  with  water  at 
100°  C.,  .910  to  .915.  The  specific  gravity  of  other 
fats  used  for  adulterating  butter  is  slightly  lower 
than  that  of  butter.  A  normal  specific  gravity  is 
a  definite  characteristic  of  genuine  butter.  The 
specific  gravity,  melting  point,  and  general  physical 
properties  of  butter  fat  are  different  from  those  of 
any  other  fat. 


CHAPTER  IV 

THE  LACTOMETER  AND  ITS  USE  IN  DETERMINING 
MILK  ADULTERATION 

42.  Quevenne's  Lactometer.  —  The  lactometer  is  a 
piece  of  apparatus  used  for  determining  the  specific 
gravity  of  milk.  It  consists  (see  Fig.  11)  of  a  bulb 
weighted  with  mercury  attached  to  a  glass  tube  of 
cylindrical  form  provided  with  a  graduated  stem, 
which  enables  the  operator  to  determine  the  depth 
to  which  the  instrument  sinks  in  milk.  Numbers 
registered  on  the  lactometer  scale  range  from  15  to 
40.  These  are  called  the  lactometer  degrees.  If 
the  lactometer  sinks  to  a  depth  of  31  on  the  scale,  it 
means  that  the  milk  has  a  specific  gravity  of  1.031. 
In  normal  milk  the  lactometer  shows  a  specific  gravity 
of  1.029  to  1.034.  Between  each  of  the  numbered 
divisions,  as  25  to  30,  there  are  five  subdivisions, 
which  enable  the  operator  to  read  to  a  .001  on  the 
specific  gravity  scale,  or  less  if  care  is  taken  in  the 
observations. 

There  are  other  forms  of  lactometers  in  use,  but 
the  Quevenne's  is  generally  preferred  because  of  its 
greater  accuracy.  A  lactometer  should  always  be 
provided  with  a  thermometer  in  order  that  the  nec- 
essary corrections  for  temperature  of  the  lactometer 
readings  may  be  made. 


DAIRY  CHEMISTRY 


43.   The  Specific  Gravity  of  Milk.  —  If  a  can  holds 
100  pounds  of  water,  to  fill  it  with  milk  would  require 
about  103.2  pounds.     This  is   because 
milk  has  a  greater  specific  gravity  than 
water.     By   the   specific   gravity    of   a 
material  is  meant  the  weight  of  a  given 
volume  compared  with  the  weight  of  an 
equal  volume  of  water  under  the  same 
conditions.     Milk  has  a  higher  specific 
gravity  than  water  because  it  contains 
*•   in  solution  a  number  of  substances,  as 
sugar,  ash,  casein,  and  albumin,  which 
increase  the  weight  of  an  equal  volume 
of  milk,  causing  it   to   have  a  higher 
specific  gravity.     The  fat  of  milk,  on 
the  other  hand,  which  is  lighter  than 
water,   has    a    tendency   to   lower    the 
specific  gravity.     As  stated  in  a  previ- 
ous chapter,  the  specific  gravity  of  milk 
fat  is  about  .91.     Since  the  amount  of 
sugar,  ash,  casein,  and  albumin  in  differ- 
ent samples  of  milk  is  fairly  constant, 
it  follows  that  the  specific  gravity  of 
the  milk  serum  is  quite  constant.    Since 
the   variations   in    the   fat   content   of 
FIG  11  —  Que-  milk  range  between  3  and  6  per  cent,  it 
venne's    lac-  follows  that  the  variations  in  the  gravity 
of  milk  are  due  largely  to  the  variations 
in  the  fat  content.     Since  the  milk  fats  vary  between 
known  limits,  the  specific  gravity  of  normal  milk 


THE  LACTOMETER   AND  ITS   USE  37 

varies  between  definite  limits.  The  lowest  specific 
gravity  of  normal  milk  is  1.029,  while  the  highest 
specific  gravity  is  1.034.  The  richer  a  sample  of  milk 
in  casein,  milk  sugar,  and  ash,  the  greater  its  buoyant 
power  and  the  higher  specific  gravity,  which  results 
in  the  lactometer  stem  not  sinking  to  so  great  a  depth 
as  it  would  if  less  casein,  sugar,  and  ash  were  present. 
Hence  we  find  skim  milk  having  a  greater  specific 
gravity  than  normal  milk.  On  the  other  hand,  the 
addition  of  water  to  milk  lowers  the  specific  gravity 
below  1.029  almost  proportionally  with  the  amount 
of  water  added.  Milks  very  rich  in  fat  have  a  lower 
specific  gravity  than  milks  which  contain  less  fat. 
This  is  due  to  the  additional  fat  in  the  milk  lowering 
its  specific  gravity.  A  skilled  operator  can  readily 
determine  whether  the  increase  or  decrease  in  the 
specific  gravity  of  milk  is  due  to  variation  in  the 
water  or  the  fat  content  of  the  milk. 

44.  Influence  of  Temperature.  —  Whenever  a  lac- 
tometer reading  is  made,  the  temperature  of  the  milk 
should  also  be  recorded,  because  a  variation  of  10° 
in  temperature  affects  the  lactometer  reading  to  the 
extent  of  1°.  When  milk  is  cold,  it  is  contracted  in 
volume  and  the  lactometer  does  not  sink  to  as  great 
a  depth  as  if  the  milk  were  warm.  This  results  in 
the  lactometer  recording  a  high  specific  gravity. 
On  the  other  hand,  if  the  milk  is  too  warm,  it  is  ex- 
panded, which  has  the  effect  of  diluting  the  milk, 
causing  the  lactometer  to  sink  to  a  greater  depth 
and  a  lower  specific  gravity  to  be  secured.  In  mak- 


38  DAIRY  CHEMISTRY 

ing  corrections  for  temperature,  the  following  general 
rule  can  be  applied  :  When  the  temperature  is 
greater  than  60°  F.,  add  .1  of  a  lactometer  degree  for 
each  degree  of  temperature,  and  when  less  than  60°  F., 
subtract  .1  for  each  lactometer  degree.  This  gen- 
eral rule  will  apply  only  for  a  variation  of  15  degrees 
either  above  or  below  the  temperature  of  60°.  In 
case  more  accurate  corrections  for  variation  in  tem- 
perature are  desired,  these  will  be  found  in  the  tables 
in  the  appendix. 

45.  Other  Lactometers.  —  The  New  York  Board  of 
Health  lactometer  is  graduated  into  120°.  The  100 
mark  represents  milk  with  a  specific  gravity  of 
1.029;  milk  with  a  lower  gravity  shows  a  reading 
of  less  than  100  on  the  lactometer  scale,  the  per- 
centage being  somewhat  proportional  to  the  amount 
of  water  added,  a  reading  of  75  indicating  that  the 
milk  is  75  per  cent  pure,  while  a  reading  of  more 
than  100  indicates  that  the  milk  is  above  legal 
standard  as  to  fat  content.  These  readings  are,  in 
general,  proportional  to  the  character  of  the  milk 
and  show  whether  extensive  adulterations,  as  skim- 
ming or  watering,  have  been  practiced.  But,  con- 
sidered alone,  the  lactometer  results  obtained  by 
either  the  Quevenne  or  the  New  York  Board  of 
Health  lactometer  are  liable  to  error,  not  on  account 
of  any  imperfection  in  the  principle  or  the  instru- 
ment, but  because  of  the  complexity  of  the  composi- 
tion of  milk.  When,  for  purposes  of  comparison,  it 
is  desired  to  change  the  readings  of  the  New  York 


THE  LACTOMETER  AND  ITS   USE 


39 


Board  of  Health  lactometer,  multiply  the  readings 
by  .29.  In  reading  the  lactometer,  the  point  to 
which  it  sinks  in  milk  should  be  carefully  noted. 
Because  of  capillary  attraction,  a  meniscus  or  curved 
surface  is  formed  on  the  surface  of  the  liquid.  The 
point  at  which  the  reading  should  be  made  is  on  a 
level  with  the  liquid  and  not  at  the  top  of  the  miscus. 
46.  Influence  of  Skimming  and  Watering.  —  Since 
milk  has  a  specific  gravity  varying  from  1.029  to  1.034, 
it  follows,  as  previously  stated,  that  any  addition  of 
water  necessarily  lowers  the  specific  gravity,  and  any 
removal  of  the  fats  necessarily  raises  the  gravity. 


FIG.  12.  —  Position  of  lactometer  iu  normal,  skimmed,  and  watered 
milk. 

Watered  milk  often  has  a  specific  gravity  of  1.035. 
When  skimming  alone  or  watering  has  been  prac- 
ticed, it  is  easily  detected  by  means  of  the  lactom- 
eter ;  but  .when  milk  is  both  skimmed  and  watered, 
the  lactometer  results  fail  to  reveal  the  fact.  The 


40  DAIRY  CHEMISTRY 

water  lowers  the  gravity,  and  the  removal  of  the  fat 
raises  it,  so  that  milk  which  has  been  both  skimmed 
and  watered  may  have  the  same  gravity  as  normal 
milk.  This  double  fraud,  however,  is  easily  detected 
when  the  Babcock  test  is  used  jointly  with  the  lac- 
tometer. 

47.  Calculation  of  Solids  in  Milk.  —  The  proportion 
in  which  the  various  solids  are  present  in  milk 
directly  influences  both  the  lactometer  readings  and 
the  results  obtained  with  the  Babcock  test.  The 
solids  not  fat  (casein,  albumin,  sugar,  and  ash)  in- 
crease uniformly  at  the  rate  of  .25  per  cent  for  each 
lactometer  degree,  and  .02  of  a  per  cent  for  each  per 
cent  of  fat.  This  general  relationship  between  the 
fat  in  milk  and  the  solids  not  fat  has  been  studied  by 
a  number  of  investigators,  notably  Richmond,  Fleisch- 
mann,  and  Babcock,  who  have  proposed  various  for- 
mulas for  the  determination  of  the  solids  in  milk. 
Babcock's  formula  is  as  follows  :  — 


Solid. 


When  this  formula  is  applied  to  a  large  number  of 
observations,  it  will  be  noted  that  "the  solids  not 
fat  increase  uniformly  at  the  rate  of  .25  per  cent  for 
each  lactometer  degree  and  .02  per  cent  for  each 
per  cent  of  fat."  This  is  also  practically  the  basis 
of  Hehner  and  Richmond's  formula.  They  found 
that  the  calculated  solids  were  uniformly  about  .14 
of  a  per  cent  less  than  those  obtained  by  chemical 


THE  LACTOMETER  AND  ITS   USE  41 

analysis.  Hehner  and  Richmond  have  proposed  the 
following  formula :  — 

Total  solids  in  milk  =—  + 17  x  1.2  +  .14. 
4 

In  order  to  apply  the  formula,  divide  the  lactometer 
number  or  lactometer  degrees  by  4.  Multiply  the  per 
cent  of  fat  found  by  test  by  1.2.  To  the  sum  of  the 
two  results  add  .14. 

EXAMPLE.  A  milk  tests  4  per  cent  fat  and  has  a  spe- 
cific gravity  of  1.033.  Hence  the  gravity  number  is  33. 
4  x  1.2  =  4.8.  33  -f-  4  =  8.22.  4.8  +  8.22  +  .14  =  13.16 
per  cent  solids.  This  milk  contains  approximately 
13.16  per  cent  solids. 

48.   Joint  Use  of  Lactometer  and  Babcock  Test.  — 

When  used  jointly,  the  quality  of  the  milk  and  the 
extent  to  which  any  adulteration  may  have  been 
practiced  can  be  accurately  determined.  The  fol- 
lowing general  rules  will  aid  in  determining  the 
quality  of  milk  :  A  low  fat  and  a  high  specific  gravity 
indicate  skimming  or  removal  of  fats.  A  low  fat 
and  a  low  specific  gravity  indicate  the  addition  of 
water.  A  low  fat  and  a  normal  specific  gravity  indi- 
dicate  that  the  milk  has  been  both  skimmed  and 
watered.  While  if  there  is  a  normal  fat  and  a  nor- 
mal gravity,  it  is  safe  to  conclude  that  the  milk  has 
been  neither  skimmed  nor  watered. 

In  order  to  determine  the  extent  to  which  adultera- 
tion may  have  been  practiced,  the  total  solids  of  the 
milk  should  be  calculated  by  Hehner  and  Richmond's 


42  DAIRY  CHEMISTRY 

formula.  By  deducting  the  percentage  of  fat,  the 
solids  not  fat  are  obtained  ;  or  the  solids  not  fat 
may  be  determined  directly  by  multiplying  the  fat 
by  .2  instead  of  by  1.2,  as  given  in  the  formula.  The 
per  cent  of  solids  not  fat  in  milk  can  also  serve  as  the 
basis  for  determining  the  extent  of  adulteration.  In 
average  milk  the  solids  not  fat  are  about  9  per  cent. 
If  the  solids  not  fat  are  found  by  calculation  to  be 
7.5,  they  are  1.5  less  than  found  in  normal  milk,  or 
if,  or  16|  per  cent,  indicating  that  at  least  16|  per 
cent  of  water  has  been  added  to  the  milk.  The  laws 
in  regard  to  the  solids  and  fat  content  of  milk  vary 
in  different  states.  In  this  state  (Minnesota)  the 
legal  standard  of  milk  is  13  for  solids  and  3^  for  fat. 
Hence  the  solids  not  fat  are  9.5.  On  the  basis  of 
the  Minnesota  standard,  this  milk  would  be  f{[,  or 
about  21  per  cent,  below  the  legal  standard.  While 
the  milk  may  not  have  been  watered  to  the  full  ex- 
tent of  21  per  cent,  it  is  21  per  cent  below  the  legal 
standard  for  milk. 


CHAPTER  V 

MILK   SUGAR  AND  LACTIC  ACID 

49.  Physical  Properties  of  Milk  Sugar.  —  Milk  sugar, 
or  lactose,  is  present  in  milk  to  the  extent  of  about 
5  per  cent.     When  milk  sours,  the  sugar  is  converted 
during  the  process  of  fermentation  into  lactic  acid, 
and  hence  the  milk  sugar  takes  an  important  part 
indirectly  in  all  dairy  operations.      Milk  sugar  is 
not  as  soluble  in  water  as  cane  sugar.     It  has  about 
the  same  chemical  composition  as  cane  sugar,  but 
differs  from  it  in  all  of  its  physical  and  chemical 
properties.     In  butter  and  cheese  making  the  main 
function  of  milk  sugar  is  the  production  of  lactic 
acid. 

50.  Fermentation  of  Milk  Sugar.  —  Under  favor- 
able conditions  milk  sugar  undergoes  lactic  acid  fer- 
mentation.    This  change  is  brought  about  by  the 
action  of  minute  organisms  known  as  the  lactic  acid 
ferments.     The  conditions  necessary  for  lactic  acid 
fermentation    are :    favorable    temperature,    70°    to 
90°  F.,  and  the  presence  of  the  ferment  body.     The 
lactic  acid  ferments  gain  access  to  the  milk  through 
the  dust  particles  of   the   air,  from   unclean  dairy 
utensils,  and   from    other    sources.     The   spores   or 
seeds  of  the  lactic  acid  organisms  readily  develop  in 

43 


44  DAIRY  CHEMISTRY 

milk,  and  as  a  result  the  milk  sugar  undergoes  a 
chemical  change  with  the  production  of  lactic  acid. 
The  milk  sugar  is  first  split  up  into  two  other  sugars, 
dextrose  and  galactose,  and  these  sugars  are  then 
changed  into  lactic  acid.  One  molecule  of  milk 
sugar  may  produce  either  two  or  four  molecules  of 
lactic  acid,  depending  upon  the  nature  of  the  fermen- 
tation change  which  takes  place.  In  addition  to  the 
lactic  acid  ferments,  there  are  a  great  many  others 
that  may  gain  access  to  milk,  develop  there,  and  cause 
various  changes  to  take  place.  The  action  of  these 
ferments  will  be  discussed  in  another  chapter  of  this 
work. 

51.  Production  of  Lactic  Acid  in  the  Milk.  —  Fresh 
milk,  even  when  first  drawn  from  the  cow,  gives  a 
slightly  acid  reaction,  due  to  the  acid  character  of 
the  casein  and  to  the  composition  of  the  mineral 
matter  or  ash  of  the  milk.  In  a  few  hours,  if  left 
exposed  to  the  air,  milk  readily  increases  its  acid 
content  until  a  sour  taste  is  developed.  The  milk 
then  contains  from  .3  to  .4  of  a  per  cent  of  lactic 
acid.  If  the  milk  contains  .4  of  a  per  cent  of  acid, 
it  will  curdle  when  boiled.  The  fermentation  usu- 
ally continues  until  .6  to  .8  of  a  per  cent  of  acid  is 
developed,  and  then  the  lactic  acid  ferments  become 
inactive.  The  products  of  the  lactic  acid  ferments 
are  destructive  to  themselves.  The  amount  of  acid  in 
milk  is  directly  proportional  to  its  freshness,  and  for 
many  purposes  milk  with  more  than  .1  of  a  per  cent 
of  acid  is  not  suitable.  The  rapidity  with  which  the 


MILK  SUGAR   AND  LACTIC  ACID 


45 


fermentation  takes  place  is  entirely  dependent  upon 
the  temperature  and  other  conditions  to  which  the  milk 
is  subjected. 

52.    Determining  the  Acidity  of  Milk. — The  methods 
employed  in  chemical  analysis   for  determining  the 


FIG.  13.  —  Apparatus  for  testing  acidity  of  milk. 

per  cent  of  acid  present  in  other  materials  are  also 
applicable  to  milk.  The  lactic  acid  that  is  developed 
in  the  souring  of  milk  belongs  to  a  general  class  of 
bodies  —  acids  —  that  are  capable  of  uniting  with  or 
being  neutralized  by  substances  known  as  alkalies. 
A  definite  amount  of  an  acid  will  always  require  a 


46  DAIRY  CHEMISTRY 

dafinite  and  known  amount  of  an  alkali  for  purposes 
of  combination  or  neutralization.  In  determining  the 
acidity  of  milk,  it  is  necessary  to  determine  simply 
the  amount  of  alkali  required  to  combine  with  and 
neutralize  all  of  the  acid  present,  changing  it  to  the 
class  of  compounds  known  as  salts.  For  this  pur- 
pose a  standard  alkali  solution  is  required.  A  tenth 
normal  solution  of  sodium  hydrate  is  usually  em- 
ployed for  the  purpose.  The  following  pieces  of 
apparatus  are  required  :  one  50  cc.  burette  gradu- 
ated to  .1  cc.;  a  burette  holder  or  support;  glass 
beakers  or  earthenware  cups  ;  one  25  or  50  cc.  pipette. 
Phenolphthalein  is  used  as  an  indicator.  In  an  acid 
solution  phenolphthalein  is  colorless,  while  in  a  weak 
alkaline  solution  it  gives  a  pink  color  and  in  a 
stronger  alkaline  solution  a  red  color.  This  indicator 
is  prepared  by  dissolving  10  gms.  of  the  powder  in 
250  cc.  of  90  per  cent  alcohol. 

The  acidity  is  determined  in  the  following  way  : 
measure  with  the  pipette  50  cc.  of  the  milk  into  a 
glass  beaker  or  porcelain  cup.  In  case  distilled  or 
soft  water  is  available,  an  equal  amount  is  added  to 
the  measured  milk  ;  5  to  7  drops  of  the  indicator 
are  added,  and  then  the  standard  alkali  from  a 
burette  a  little  at  a  time,  until  the  color  of  the  milk 
upon  stirring  is  changed  to  a  faint  pink.  Before 
adding  the  alkali  the  height  of  the  liquid  in  the 
burette  should  be  recorded,  and  at  the  close  of  the 
operation  it  should  be  read  again  in  order  to  deter- 
mine the  number  of  cubic  centimeters  required  to 


MILK  SUGAR  AND  LACTIC  ACID  47 

neutralize  the  acid  in  the  milk.  The  amount  ol 
alkali  used  will  vary  directly  with  the  amount  of 
acid  in  the  milk,  milks  of  high  acidity  requiring  a 
large  amount  of  alkali.  The  alkali  is  prepared  by 
dissolving  4  gm.  of  pure  sodium  hydrate  or  5.6 
gm.  of  pure  potassium  hydrate  in  a  liter  of  distilled 
water.  This  standard  alkali  should  be  prepared  only 
by  a  chemist.  The  alkali  must  be  kept  in  glass- 
stoppered  bottles  protected  from  the  air,  and  when 
used  it  should  not  be  diluted. 

53.  Calculating  the  Acidity  of  Milk.  —  Each  cubic 
centimeter  of  alkali  neutralizes  .009  gm.  of  lactic 
acid.  In  case  50  cc.  of  milk  are  used  andi  20  cc.  of 
alkali  required  to  produce  the  pink  color,  the  per 
cent  of  lactic  acid  in  the  milk  will  be  found  as 
follows  :  — 

•°09  x  20  x  100  =  .36  per  cent. 
oO 

In  case  a  different  quantity  than  50  cc.  of  milk  is 
used,  then  substitute  the  number  of  cubic  centimeters 
of  the  sample  tested  for  the  50  in  the  formula.  The 
test  can  be  satisfactorily  made  with  either  a  25  or  a 
20  cc.  sample,  and  if  desired  a  17. 6  cc.  pipette  can  be 
used.  In  case  a  20  cc.  pipette  is  used  for  measur- 
ing the  milk,  then  the  number  of  cubic  centimeters 
of  alkali  can  be  multiplied  by  .045  and  the  per  cent 
of  acid  obtained  directly.  In  making  the  test,  the 
operator  should  cease  adding  the  alkali  as  soon  as  a 
permanent  pink  color  is  obtained.  When  the  alkali 


48  DAIRY  CHEMISTRY 

is  first  added  and  the  milk  is  stirred,  the  color  is  not 
permanent,  but  after  a  sufficient  amount  of  alkali  is 
added,  a  point  is  reached  when  two  or  three  drops 
more  will  produce  a  permanent  color.  In  making 
comparative  tests,  the  operator  should  always  aim  to 
secure  the  same  degree  of  color  in  all  the  samples 
tested,  Strong  alkali  water  is  not  suitable  for  wash- 
ing the  milk  dishes  or  for  diluting  the  milk  in  mak- 
ing this  test. 

54.  Alkaline  Tablets.  —  Because  of  the  difficulty  in 
preparing  and  securing  the  tenth  normal  solution, 
Farrington  and  others  have  proposed  the  use  of 
alkaline  tablets.  These  tablets  are  so  prepared  as  to 
contain  a  definite  quantity  of  alkali  mixed  with  the 
requisite  indicator  or  coloring  matter.  When  used, 
the  tablets  are  to  be  dissolved  in  pure  rain  or  distilled 
water.  To  prepare  the  ordinary  tablet  solution 
five  are  placed  in  a  100  cc.  glass-stoppered  cylinder 
filled  with  97  cc.  of  water,  and  when  dissolved  this 
gives  an  alkali  solution  of  the  requisite  strength. 
In  making  the  test,  17.6  cc.  of  milk  or  cream  is 
measured  into  a  porcelain  cup,  and  the  alkali  solution 
added  from  the  cylinder  until  the  pink  color  becomes 
permanent.  The  amount  of  the  tablet  solution  used 
is  found  by  reading  the  amount  of  solution  remain- 
ing in  the  cylinder  and  subtracting  it  from  the  origi- 
nal quantity.  The  number  of  cubic  centimeters  of 
tablet  solution  used,  divided  by  100,  gives  directly 
the  percentage  of  acid  in  the  sample.  If  17.6  cc.  of 
cream  requires  40  cc.  of  tablet  solution  to  produce 


MILK  SUGAR  AND  LACTIC  ACID  49 

the  pink  color,  then  the  sample  of.  cream  contains  .4 
per  cent  lactic  acid. 

55.  Acidity  of  Cream. — Cream  that  is  suitably 
ripened  for  churning  should  contain  about  .5  of  a 
per  cent  of  lactic  acid.  If  the  cream  contains  more 
than  .6  per  cent  of  acid,  it  is  liable  to  cause  coagula- 
tion of  the  casein  and  formation  of  clots  in  the  cream, 
and  when  churned,  mottled  butter  is  produced.  The 
acid  test  will  be  found  valuable  in  butter  making 
as  a  means  of  producing  a  uniform  product,  which 
is  accomplished  by  having  the  cream  each  day  of  the 
same  degree  of  ripeness,  and  churning  under  uniform 
conditions.  Any  of  the  methods  described  for  deter- 
mining the  acidity  of  cream  will  be  found  helpful 
in  producing  a  uniform  butter  product. 


CHAPTER   VI 
CREAM 

56.  Composition  of  Cream. — Cream  is  character- 
ized by  containing  a  higher  percentage  of  fat  than 
milk.  Average  cream  contains  from  18  to  25  per 
cent  of  fat ;  some  samples  may  contain  as  low  as 
8  per  cent  and  others  as  high  as  50  per  cent.  From 
75  to  85  per  cent  of  the  solid  matter  of  cream  is  fat. 
The  percentage  of  ash,  sugar,  casein,  and  albumin  is 
slightly  less  than  in  milk.  The  composition  of 
average  cream  is  about  as  follows  :  — 

PER  CENT 

Water 66.41 

Solids 33.59 

Fat 25.72 

Casein  and  albumin 3.70 

Milk  sugar 3.54 

Ash 0.63 

Cream  is  spoken  of  as  thick,  medium,  or  thin,  accord- 
ing to  its  fat  content ;  thin  cream  contains  from  8 
to  15  per  cent  of  fat,  and  thick  cream  above  35  per 
cent.  One  hundred  pounds  of  milk  will  produce 
from  15  to  22  pounds  of  cream,  depending  upon  the 
way  in  which  the  cream  is  obtained,  and  also  upon 
the  composition  of  the  milk.  In  many  states  and 
50 


CREAM  51 

countries  the  percentage  of  fat  which  the  cream 
should  contain  is  designated  by  law.  In  Min- 
nesota legal  cream  should  contain  20  per  cent 
of  fat. 

In  the  creaming  of  milk,  the  larger  globules  are 
more  completely  separated,  and  consequently  the 
cream  contains  a  higher  percentage  of  large  fat 
globules  than  milk,  the  smaller  fat  globules  being 
present  in  greatest  proportion  in  the  skim  milk. 
There  is  also  a  slight  mechanical  separation  of  the 
milk  proteids  during  the  creaming  process,  resulting 
in  the  casein  and  albumin  being  present  in  a  different 
proportion  in  cream  than  in  milk.  When  milk  is 
creamed  by  gravity  process,  chemical  changes  take 
place,  resulting  in  the  cream  containing  more  acid 
than  the  milk,  and  the  proteids  having  a  different 
composition. 

57.  Testing  Cream.  —  Cream  containing  from  8  to 
15  per  cent  of  fat  can  be  tested  by  the  Babcock  test 
in  the  same  general  way  as  milk.  It  will  be  neces- 
sary, however,  to  divide  the  17.6  cc.  of  cream  into 
two  test  bottles  and  to  rinse  the  pipette  with  a  small 
amount  of  warm  water  to  completely  remove  all  of 
the  fat,  so  that  each  test  bottle  will  contain  about 
18  cc.  of  liquid.  The  amount  of  fat  obtained 
in  the  two  bottles  is  added  together,  to  give  the 
approximate  amount  of  fat  in  the  cream  tested. 
For  the  testing  of  cream  special  test  bottles  have 
been  devised  known  as  the  Bartlett  and  the  Winton 
(see  Figs.  14  and  15).  The  Bartlett  cream  test  bottle 


52 


DAIRY  CHEMISTRY 


is  similar  to  the  Babcock  test  bottle,  except  that  it  is 
provided  with  a  bulb  in  the  stern  to  accommodate 
the  additional  fat  from  the  cream.  In  using  this 
bottle,  care  should  be  exercised  that  the  right 
amount  of  water  is  added  _ 

so  as  to  leave  a  sufficient 
amount  of  fat  both  above 
and  below  the  bulb  for  the 
purpose  of  reading.  The 
Winton  test  bottle  is  pro- 
vided with  a  larger  gradu- 
ated neck  than  the  ordinary 
test  bottle. 

In  the  testing  of  cream 
greater  care  is  necessary 
than  in  the  testing  of  milk. 
When  cream  is  measured 
with  the  pipette,  an  error 
is  introduced  into  the  work 
because  cream  has  a  lower 
specific  gravity  than  milk. 
17.6  cc.  of  cream  testing 
FIG.  14.  — Win-  25  per  cent  fat  weighs  Fio.is.-Bart- 

ton  cream  test          i  -i  -i  7  o  lett     cream 

bottle.  °nlv       about       17'2        gm'        test  bottle. 

Since  the  test  bottles  are 

made  for  18  gm.  of  milk,  the  results  are  neces- 
sarily low  when  applied  to  cream.  Farrington  and 
Woll,  in  "  Testing  Milk  and  Its  Products,"  give  the 
weight  of  cream  delivered  by  a  17.6  cc.  pipette  as 
follows  :  — 


CREAM 


53 


PER  CENT  OF  FAT  IN 
CREAM 

SPECIFIC  GRAVITY 

(17.5°  C.) 

WEIGHT  OF  CRKAM' 
DELIVERED,  GMS. 

10 

1.023 

17.9 

15 

1.012 

17.7 

20 

1.008 

17.3 

25 

1.002 

17.2 

30 

0.996 

17.0 

35 

0.980 

16.4 

40 

0.966 

16.3 

45 

0.950 

16.2 

50 

0.947 

15.8 

In  the  testing  of  cream  the  most  satisfactory 
results  are  secured  by  weighing.  This  is  done  by 
first  weighing  the  cream  test  bottle  on  a  balance 
provided  with  a  suitable  beam  for  counterpoising, 
then  adding  with  a  pipette  10  cc.  of  cream  and 
weighing  the  test  bottle  containing  the  cream  to 
determine  the  weight  of  the  cream  delivered.  A 
little  warm  water  is  then  added  to  the  test  bottle  in 
order  to  wash  down  the  cream,  and  the  test  is  com- 
pleted in  the  usual  way.  Since  the  test  bottle  is 
made  for  18  gm.  of  milk,  it  will  be  necessary  to 
multiply  the  reading  found  in  the  test  by  1.8.  In 
case  more  or  less  than  10  gm.  are  taken,  the  factor 
used  in  multiplying  is  obtained  by  dividing  the  18 
gm.  by  the  weight  of  the  cream  used.  If  a  sample 
of  cream  weighing  9.5  gm.  gives  a  reading  of  16.2, 
the  percentage  of  fat  is  :  — 

!§_><_1A2  =  30.69. 


54  DAIRY  CHEMISTRY 

Prior  to  the  introduction  of  the  Babcock  test, 
other  methods  were  employed  for  testing  the  value 
of  cream  for  butter-making  purposes.  The  oil  test 
churn  was  one  of  the  methods  most  extensively  used. 
In  operating  the  test  the  number  of  cubic  inches  of 
the  cream  sample  was  determined  by  measuring  the 
cream  in  a  cream  pail.  The  cream  was  thoroughly 
mixed  by  stirring  and  a  measured  quantity  placed  in 
a  tube  which  was  corked.  The  tube  with  others 
was  then  placed  in  a  specially  devised  churn  and  the 

cream  churned  into 
butter,  which  was 
separated  from  the 
curd  by  melting  and 
special  manipula- 
tion. The  amount 
of  butter  obtained 
in  the  tube  was 
measured  by  a  rule, 

and  the  butter  yield  of  the  cream  was  thus  deter- 
mined. This  method  of  testing  cream,  however,  has 
been  entirely  superseded  by  the  Babcock  test,  the 
cream  now  being  measured  directly  into  the  test 
bottles. 

In  the  testing  of  cream,  it  is  advisable,  unless  the 
operator  has  developed  a  high  degree  of  skill,  to 
make  duplicate  tests  and  then  take  an  average. 

58.  Methods  of  Creaming.  —  There  are  three 
methods  employed  in  the  creaming  of  milk,  —  the 
gravity  process,  cold  deep  setting,  and  the  cream 


CREAM  55 

separator.  In  the  gravity  process,  the  milk  is  usu- 
ally placed  in  shallow  pans  and  allowed  to  remain  in 
a  room  at  a  temperature  of  about  60°  for  24  or  36 
hours,  until  the  cream  is  separated  by  gravity. 
When  this  process  of  creaming  is  followed  the  losses 
of  fat  are  usually  greater  than  by  any  other  method. 
The  losses  are  especially  heavy  when  the  cows  are 
well  advanced  in  their  period  of  lactation.  While  it  is 
possible  to  do  reasonably  effectual  creaming  by  the 
gravity  process,  the  losses  of  fat  are  frequently  ex- 
cessive, amounting  to  from  25  to  30  per  cent,  and 
more,  of  the  total  fat  in  the  milk,  the  skim  milk 
often  containing  from  .6  to  1  per  cent  of  fat. 

In  the  cold  deep  setting  process  the  milk  is  set  in 
deep  pails,  which  are  immersed  in  water  of  a  temper- 
ature of  40°  to  44°  F.  At  the  end  of  12  hours 
the  process  of  creaming  is  completed  and  the  skim 
milk  will  usually  contain  from  .2  to  .4  of  a  per  cent 
fat.  For  the  creaming  of  milk  by  the  cold  deep  set- 
ting process,  it  is  necessary  that  the  water  in  which 
the  milk  is  immersed  be  kept  at  a  low  temperature. 
The  creaming  commences  immediately  when  the  milk 
is  placed  in  the  water.  The  milk  in  the  bottom  of  the 
can  first  becomes  poorer  in  fat,  then  the  middle  layer 
is  affected,  and  finally  the  upper  layer.  The  tem- 
perature of  the  water  at  the  time  the  milk  is  set  is 
of  greater  importance  than  the  temperature  of  the 
milk.  A  difference  of  10°  in  the  temperature  of  the 
milk  will  not  affect  the  efficiency  of  the  creaming, 
but  a  difference  of  5°  in  the  temperature  of  the 


56 


DAIRY  CHEMISTRY 


water  will  seriously  affect  the  thoroughness  of  the 
process.  It  is  not  possible  by  prolonging  the  process 
to  make  up  in  efficiency  of  creaming  for  the  loss 
sustained  by  the  want  of  a  low  temperature  at  the 
beginning.  There  is  quite  a  noticeable  difference 
in  the  way  in  which  two  milks  may  respond  to 
creaming  by  the  cold  deep  setting  process.  The 
rapidity  with  which  the  process  takes  place  when 
the  conditions  are  favorable  and  the  effect  of  less 
favorable  conditions  may  be  observed  from  the  fol- 
lowing table :  — 


GOOD  CONDITIONS 

POOR  CONDITIONS 

A    E      60 

Per  cent 

Per  cent 

Fat  in  milk 

5.00 

4.45 

Top  below  4  inches,  30  minutes 

4.60 

4.40  ' 

Middle,                       30  minutes 

4.45 

4.40 

Bottom,                      30  minutes 

3.40 

4.40 

Top,                              1  hour 

4.00 

4.30 

Middle,                         1  hour 

3.85 

4.30 

Bottom,                        1  hour 

1.30 

2.92 

Top,                              2  hours 

3.30 

3.90 

Middle,                         2  hours 

2.10 

3.90 

Bottom,                        2  hours 

0.75 

2.40 

Top,                            5$  hours 

1.40 

3.00 

Middle,                       5j  hours 

1.00 

2.90 

Bottom,                      5£  hours 

0.35 

2.18 

Top,                           10  hours 

0.40 

2.52 

Middle,                       10  hours 

0.30 

2.40 

Bottom,                      10  hours 

0.15 

1.40 

Average  fat  in  skim  milk 

0.25 

1.40 

CREAM  57 

When  milk  is  creamed  by  the  separator,  the  losses 
of  fat  may  be  reduced  to  less  than  .1  of  one  per  cent, 
and  they  are  occasionally  less  than  .05  of  one  per  cent. 
The  principle  involved  in  the  creaming  of  milk  by 
means  of  the  cream  separator  is  explained  in  Section 
21.  There  are  a  great  many  different  kinds  of  sepa- 
rators in  use.  In  determining  the  efficiency  of  a 
separator,  the  amount  of  fat  left  in  the  skim  milk  is  the 
main  factor  to  consider.  In  the  manufacture  of  butter, 
the  losses  of  fat  in  the  skim  milk  exceed  the  losses 
in  all  other  ways.  This  is  because  the  amount  of  skim 
milk  is  large  compared  with  the  amount  of  butter- 
milk, and  a  loss  of  .1  of  a  per  cent  of  fat  in  the 
skim  milk  amounts  to  a  much  greater  total  loss  than 
.2  of  a  per  cent  of  fat  in  the  buttermilk.  For  thor- 
ough creaming  at  least  98  per  cent  of  the  total  fat  in 
the  milk  should  be  recovered  in  the  cream.  In  the 
creaming  of  milk  by  the  separator,  the  dirt,  slime, 
and  foreign  matter  which  milk  may  contain  are 
largely  removed  in  the  separator  slime  ;  this  results 
in  the  production  of  a  better  quality  of  cream  for 
butter  making  than  that  secured  by  the  cold  deep 
setting  process.  Cream  obtained  by  the  separator 
has  practically  the  same  composition  as  that  obtained 
by  other  processes.  But  cream  obtained  by  the  grav- 
ity and  cold  deep  setting  processes  is  usually  in 
a  more  advanced  stage  of  ripeness  than  separator 
cream. 

When  milk  is  creamed  by  the  separator,  the  com- 
position of  the  cream  can  be  regulated  by  the  flow 


58  DAIRY  CHEMISTRY 

of  the  milk  and  the  adjustment  of  the  cream  outlet. 
The  condition  of  the  milk  as  to  temperature  at  the 
time  of  separating  influences  the  efficiency  of  the 
creaming.  If  the  milk  is  too  cold,  too  large  an 
amount  of  fat  is  left  in  the  skim  milk.  The  tem- 
perature of  the  milk  at  separation  should  range  from 
75°  to  90°  F.,  depending  largely  upon  the  individual- 
ity of  the  milk.  It  will  be  necessary  to  separate 
some  milks  at  a  higher  temperature  than  others  on 
account  of  the  fat  globules  containing  a  larger  pro- 
portion of  stearin,  palmitin,  and  hard  fats.  The 
temperature  should  be  the  lowest  that  will  show  the 
least  loss  of  fat  in  the  skim  milk,  so  as  to  avoid  any 
unnecessary  heating  of  the  milk.  For  data  in  regard 
to  trials  of  different  separators  and  the  amount  of 
fat  left  in  the  skim  milk,  the  reader  is  referred  to 
the  bulletins  of  the  various  agricultural  experiment 
stations,  particularly  those  of  the  Vermont,  New 
York,  and  Wisconsin  Stations. 

59.  Adulteration  of  Cream.  —  Cream  is  adulterated 
by  the  addition  of  milk,  coloring  matter,  preserva- 
tives, and  materials  to  give  the  cream  a  higher  vis- 
cosity. The  preservatives  used  are  formalin,  boric 
acid,  and  salicylic  acid.  The  coloring  matters  are 
similar  to  those  used  for  the  coloring  of  butter,  just 
a  sufficient  amount  being  used  to  give  the  cream  a 
yellow  tinge  suggesting  a  high  fat  content.  In 
order  to  impart  viscosity,  the  material  known  as  vis- 
cogin,  consisting  of  a  solution  of  lime  in  cane  sugar, 
is  sometimes  used.  This  causes  the  cream  to  appear 


CREAM  .       59 

to  have  a  higher  fat  content  by  increasing  its  viscos- 
ity. Cream  of  low  fat  content  is  the  most  frequent 
form  of  fraud  practiced. 

60.  The   Ripening   of   Cream.  —  Before   churning, 
cream  is  usually  allowed  to  undergo  the  process  of 
ripening  so  as  to  secure  more  complete  churning  of 
the  cream  and  produce  a  better  quality  of  butter. 
The  cream  is  placed  in  vats  and  warmed  to  a  tem- 
perature of  60°  to  70°  F.,  so  as  to  allow  the  develop- 
ment of  the  lactic  acid  ferments.     The  ripening  of 
the  cream  is  frequently  hastened  by  the  addition  of 
a  small  amount  of  sour  milk  especially  prepared  and 
known  as  a"  starter."    In  the  ripening  of  the  cream, 
it  should  be  the  aim  to  allow  the  lactic  acid  ferments 
to  develop  and  to  prevent  as  far  as  possible  other 
kinds  of  fermentation  from  taking  place  by  having 
the  milk  as  clean  and  pure  as  possible  before  cream- 
ing, so  other  ferment  bodies  cannot  gain  access  to 
either  the  milk  or  the  cream,  and  by  the  use  of  a 
pure   culture   or    starter.       When   the    cream    has 
reached  the  proper  degree  of  acidity,  determined  by 
the  lactic  acid  test  (see  Sec.  52),  it  is  in  condition  to 
churn.      In  the  handling  of  cream  any  change  of 
temperature  should  be  gradual,  as  sudden  heating 
or   cooling  may  seriously  affect  the  quality  of   the 
butter. 

61.  The  Use  of  Pure  Cultures.  —  In  order  to  secure 
the  best  results,  particular  care  should  be  given  to  the 
preparation  and  use  of  the  culture.     In  the  ripening 
of  cream,  the  use  of  a  pure  culture  is  equally  as  im- 


60  DAIRY  CHEMISTRY 

portant  as  the  use  of  good  yeast  in  bread  making. 
The  milk  from  a  fresh  and  perfectly  healthy  cow 
should  be  used  in  preparing  the  starter,  rather  than 
the  mixed  milk  of  an  entire  herd.  In  the  prepara- 
tion and  use  of  the  culture,  scrupulous  cleanliness 
should  be  practiced,  A  number  of  commercial  cul- 
tures for  the  ripening  of  cream  have  been  placed  on 
the  market,  as  Conn's  bacillus  No.  41  and  Hanson's 
lactic  ferment.  In  the  use  of  these,  or  of  home- 
made cultures,  good  results  cannot  be  secured  unless 
the  cream  is  cared  for  and  manipulated  in  the 
proper  way.  The  best  quality  of  butter  cannot  be 
made  from  cream  that  has  been  contaminated  in  any 
way  or  contains  abnormal  ferment  bodies. 

62.  Influence  of  Delay  on  the  Creaming  of  Milk.  — 
When  milk  is  creamed  by  the  centrifugal  method, 
there  is  no  loss  of  efficiency  in  creaming  if  the  milk 
is  not  separated  at  once,  provided  the  proper  tem- 
perature is  secured  when  the  milk  is  separated. 
When  milk  is  creamed  by  the  cold  deep  setting  pro- 
cess, unnecessary  delay  should  be  avoided,  but  undue 
haste  in  placing  the  milk  in  the  tank  water  is  not 
necessary.  However,  the  milk  should  not  be  left  in 
the  barn.  Experiments  at  the  Maine  and  Cornell 
Experiment  Stations  have  shown  that  with  the 
mixed  milk  of  an  entire  herd  there  is  no  appreciable 
loss  of  fat  when  the  placing  of  the  milk  in  the  tank 
has  been  delayed  for  half  or  three  quarters  of  an 
hour.  At  the  Wisconsin  Station  experiments  showed 
that  with  three  lots  of  cows  there  was  no  loss  in 


CREAM  61 

creaming  following  a  delayed  setting,  but  with  two 
lots  a  material  loss  of  creaming  power  resulted. 

63.  Creaming   of   Mixed   Milks.  —  In    case    milk 
creams  with  difficulty  on  account  of  the  cows  being 
far  advanced  in  the  period  of  lactation,  the  creaming 
is  frequently  improved  by  mixing  such  milk  with 
that  of  fresh  cows.      Beneficial  effects  are  usually 
obtained  by  creaming  mixed  milks.      The   Babcock 
milk  test,  however,  is  the  only  safe  guide  to  follow 
in  such  cases. 

64.  Cream  Raising  by  Dilution.  —  When  either  hot 
or  cold  water  is  added  to  milk,  the  creaming  is  accel- 
erated  and   a  larger  volume  of  cream  is  obtained. 
When  the  cream  is  tested,  however,  it  will  be  found 
to  contain  a  low  per  cent  of  fat.     The  addition  of 
either  hot  or    cold  water  to  milk   produces  a  thin 
cream.     The  total  losses  of  fat  from  cream  obtained 
by  the  dilution  process  are   greater  than  when  the 
water  is  omitted.     Experiments  have  shown  that  it 
is  not  economical  to  cream  milk  by  the  addition  of 
either  large  or  small  amounts  of  hot  or  cold  water. 
When  hot  water  is  used,  the  cream  is  often  overripe 
before  it  is  skimmed,  and  a  smaller  amount  and  a 
poorer  quality  of  butter  are  obtained.     Any  inter- 
ference with  the  normal  process  of  creaming  usually 
results  in  the  production  of  a  large  volume  of  pool 
cream. 


CHAPTER  VII 

THE  CHEMISTRY  OF  BUTTER   MAKING 

65.  Churning.  —  When  cream  is  agitated,  the  fat 
globules  coalesce,  forming  granules  of  butter.  Vari- 
ous theories  have  been  advanced  to  explain  the 
changes  which  take  place  during  the  process  of 
churning.  It  is  believed,  however,  that  the  change 
is  largely  physical  in  character  and  that  the  agitation 
of  churning  is  necessary  in  order  to  overcome  the 
resistance  offered  by  the  serum  of  the  milk.  During 
the  process  of  churning,  the  globules  lose  their 
spherical  form  and  become  irregular  masses  of  fat. 
These  irregular  masses  more  readily  coalesce  than 
spherical  bodies.  Various  forms  of  churns  have 
been  devised  to  carry  out  different  theories  as  to 
churning.  Some  churns  have  been  provided  with 
paddles  and  special  devices  for  agitating  the  cream 
and  for  rupturing  the  membrane  in  which  the  milk 
fat  globules  were  supposed  to  be  inclosed.  With 
change  of  views  in  regard  to  theories  of  churning, 
most  of  these  devices  have  been  discarded,  and  our 
present  churns  are  much  simpler  in  construction  and 
do  not  have  special  devices  for  agitating  the  cream, 
this  being  secured  largely  by  the  concussion  during 
the  churning  process. 

The  conditions  influencing  churning  are  (1)  ripe- 


THE   CHEMISTRY  OF  BUTTER  MAKING          63 

ness  of  cream,  (2)  temperature  of  the  cream,  and 
(3)  individuality  of  the  cream  as  affected  by  period 
of  lactation,  season  of  the  year,  nature  of  the  fat, 
and  breed  characteristics. 

Ripe  cream,  containing  .5  of  a  per  cent  of  acid, 
usually  churns  more  completely  than  unripe  cream. 
It  is  believed  that  this  is  due  to  the  acid  coagulating 
the  casein  of  the  cream  serum,  thereby  reducing  the 
surface  tension  of  the  fat  globules.  The  ripeness  of 
the  cream  is  one  of  the  most  important  factors  in 
churning.  If  creams  of  different  degrees  of  ripeness 
are  combined  and  churned,  there  is  an  unevenness  in 
the  butter  product  due  to  the  mixed  cream  not  churn- 
ing evenly,  a  part  producing  butter  granules  be- 
fore the  rest  of  the  cream  has  completed  the  process 
of  churning.  If  overripe,  a  poor  quality  of  butter 
is  produced,  due  to  the  presence  of  excessive  amounts 
of  fermentation  products.  It  was  formerly  believed 
that  an  excessive  amount  of  lactic  acid  caused  a  loss 
of  butter  fat  in  churning.  It  has  been  found,  how- 
ever, that  lactic  acid  has  no  solvent  action  upon 
butter  fat.  It  should  be  the  object  to  secure  the 
same  degree  of  acidity  for  each  churning,  so  as  to  pro- 
duce as  even  a  product  as  possible.  If  cream  is  not 
sufficiently  ripened,  butter  of  poor  keeping  quality  is 
produced,  the  fermentation  changes  which  take  place 
in  the  butter  causing  it  to  have  undesirable  flavors. 
One  of  the  objects  of  the  thorough  ripening  of  cream 
is  to  prevent  further  and  undesirable  fermentation 
processes  from  taking  place  later  in  the  butter. 


64       .  DAIRY  CHEMISTRY 

The  temperature  at  which  cream  should  be  churned 
varies  from  50°  to  60°  F.,  depending  upon  the  ripe- 
ness of  the  cream  and  its  general  characteristics. 
Sweet  cream  should  be  churned  at  a  lower  tempera- 
ture (50°  to  55°)  than  ripened  cream  (58°  to  66°).  It 
is  not  possible  to  assign  a  definite  temperature  for 
churning  so  as  to  secure  the  best  results  with  all 
kinds  of  cream.  The  most  suitable  temperature  for 
the  conditions  under  which  the  butter  is  produced 
must  be  determined  by  trial.  A  preliminary  churn- 
ing can  be  made  at  a  temperature  of  60°,  the  charac- 
ter of  the  butter  noted,  and  if  it  is  too  hard  in  texture 
and  fails  to  churn  in  a  reasonable  time,  the  next 
churning  can  be  made  at  a  slightly  higher  tempera- 
ture, 62°.  If,  however,  the  butter  is  soft  in  texture 
and  churns  in  too  short  a  time,  the  temperature  has 
been  too  high.  Thick  cream  should  be  churned  at  a 
lower  temperature  than  thin  cream.  The  right 
temperature  for  churning  also  depends  largely  upon 
the  character  of  the  fat  globules.  If  the  hard  fats, 
stearin  and  palmitin,  predominate,  as  is  frequently 
the  case  when  the  cows  have  been  long  in  milk  and 
have  received  an  excess  of  coarse,  dry  fodders  with  a 
scant  amount  of  grain,  the  cream  will  have  to  be 
churned  at  a  high  temperature.  During  churning 
there  is  a  rise  in  temperature  of  two  or  three  degrees, 
due  to  the  agitation  of  the  cream,  and  when  the 
churn  is  first  started  there  is  a  slight  production  of 
gas  which  should  be  allowed  to  escape. 

The  completeness  and  ease  with  which  cream  is 


THE  CHEMISTRY  OF  BUTTER   MAKING         65 

churned,  or  its  churnability,  is  influenced  by  a  num- 
ber of  factors,  as  season  of  the  year,  food  consumed, 
period  of  lactation,  and  individuality  of  the  animals 
producing  the  milk.  When  cows  have  not  been  salted 
regularly,  the  inilk  is  not  normal  in  composition, 
and  difficulties  in  churning  frequently  arise.  The 
character  of  the  food  consumed  influences  the  com- 
position of  the  butter  fats,  which  in  turn  affects  the 
churnability  of  the  cream.  The  effect  of  the  food 
upon  the  character  and  composition  of  the  milk  will 
be  discussed  in  another  chapter  of  this  work.  When 
cows  are  advanced  in  their  period  of  lactation,  the 
globules  are  smaller  in  size,  the  milk  is  more  viscous 
in  character,  and  has  a  different  composition  from 
milk  in  the  first  stages  of  lactation.  This  affects 
the  completeness  and  rapidity  with  which  cream 
yields  to  the  churning  process.  In  churning  abnor- 
mal creams,  the  conditions  must  be  carefully  studied 
and  the  cause  of  any  difficulty  determined  ;  then  the 
temperature  of  churning,  degree  of  ripeness,  or 
other  conditions  may  be  changed  so  as  to  meet  the 
requirements  of  the  cream  in  question.  Occasion-, 
ally  abnormal  conditions  of  the  cream  affecting 
churning  are  due  to  some  form  of  fermentation 
resulting  in  the  production  of  gas  or  rendering  the 
milk  proteids  more  viscous  in  character,  which  in 
turn  affects  the  churnability  of  the  cream. 

The  process  of  churning  should  be  stopped  when 
the  butter  globules  are  granular  and  about  the  size 
of  wheat  kernels.  If  the  cream  has  been  properly 


66  DAIRY  CHEMISTRY 

ripened,  exhaustive  churning  has  been  secured  when 
the  butter  is  in  this  condition.  Excessive  churning 
may  result  in  spoiling  the  grain  of  the  butter  and 
prevent  thorough  washing  to  remove  the  buttermilk. 
The  nature  and  extent  of  the  washing  of  butter 
should  be  regulated  largely  by  the  condition  in 
which  the  butter  granules  are  found  at  the  close 
of  churning.  Ordinarily,  butter  is  washed  with 
water  at  a  temperature  of  from  45°  to  55°,  and  the 
working  continued  until  the  washings  which  drain 
from  the  butter  are  clear.  It  is  preferable  to  re- 
move the  buttermilk  as  early  as  possible  and  then 
continue  the  churning  in  a  not  too  cold  wash  water, 
rather  than  to  overchurn  the  cream  at  first.  The 
amount  of  salt  necessary  to  add  at  the  time  of  work- 
ing will  depend  largely  upon  the  market  require- 
ments ;  usually  three  quarters  to  one  ounce  of  salt 
per  pound  of  butter  will  be  sufficient.  Not  all  of 
the  salt  added  is  retained  in  the  butter  ;  a  large 
portion  of  it  is  removed  during  the  process  of  work- 
ing. From  the  amount  of  cream  churned  and  its 
richness  in  fat,  the  probable  butter  yield  can  be 
determined  ;  so  the  amount  of  salt  required  can  be 
calculated  with  a  good  degree  of  accuracy. 

66.  Dairy  Salt.  —  For  dairy  purposes  salt  of  a 
high  degree  of  purity  is  necessary.  Many  such 
salts  are  found  on  the  market,  ranging  in  purity 
from  97  to  99  per  cent,  the  principal  impurities 
being  gypsum  and  small  amounts  of  other  salts. 
Salt  should  be  entirely  soluble  in  water,  any  residue 


THE  CHEMISTRY  OF  BUTTER  MAKING         67 

being  due  to  impurities.  The  salt  crystals  should 
be  clear  and  of  medium  granulation.  If  the  crystals 
are  too  large  in  size,  overworking  of  the  butter  may 
be  necessary  in  order  to  incorporate  the  salt.  If  the 
butter  is  worked  too  dry  and  too  much  fine  salt  is 
used,  the  salt  will  separate  and  form  a  crust  on  the 
surface  of  the  butter.  A  pure  salt  will  not  become 
very  moist  when  stored  in  a  reasonably  dry  room, 
neither  will  it  form  hard  cakes  which  crush  with 
difficulty.  Salts  that  are  not  pure  may  impart  an 
undesirable  taste  and  flavor  to  the  butter. 

67.  Buttermilk.  —  Buttermilk  has  about  the  same 
general  composition  as  skim  milk.     It  is  practically 
the  skim  milk  of   cream  and  varies  in  fat  content 
with   the  exhaustiveness  of   churning.     Buttermilk 
may  contain  a  high  per  cent  of  fat,  but  ordinarily 
it  contains  .2  of  a  per  cent  or  less.     The  composi- 
tion of  buttermilk  is  generally  about  as  follows :  — 

Water 90.50 

Fat .0.20 

Casein  and  albumin 3.30 

Sugar 5.30 

Ash .        .  0.70 

If  not  overdiluted  with  wash  water,  buttermilk  has 
practically  the  same  feeding  value  as  skim  milk. 

68.  Losses  of  Fat  in  Butter  Making.  —  When  100 
pounds  of  milk  are  creamed,  about  80  pounds  of  skim 
rnilk  and  20  pounds  of  cream  are  obtained.     If  the 
milk   tests  4  per  cent   fat,  and   the  cream   is  care- 
fully churned,  it  will   make   about   4.6   pounds   of 


68 


DAIRY  CHEMISTRY 


butter.  The  following  table  shows  how  the  vari- 
ous constituents  of  100  pounds  of  milk  are  dis- 
tributed when  the  milk  is  creamed  and  made  into 
butter.  With  poor  work,  of  course,  a  much  smaller 
amount  of  fat  is  recovered  in  the  butter,  and  more  is 
lost  in  the  skim  milk  and  buttermilk. 

DISTRIBUTION  OF  MILK  SOLIDS  IN  BUTTER  MAKING 


PRODUCTS  FROM  100  Lu.  OF  MILK 

100  Ib. 
of  Milk 

20  Ib.  of 
Cream 

Skim 
Milk 

Butter 

Butter- 
milk 

Total  solids 

13.00 
4.00 
3.50 
4.75 
0.75 

5.18 
3.88 
0.50 
0.75 
0.05 

7.82 
0.12 
3.00 
4.00 
0.70 

4.00 

3.83 
0.10 
0.05 

1.18 
0.05 

0.40 
0.70 
0.03 

Fat  

Casein  and  albumin  .  . 
Sugar  and  acid  .... 
Ash  .  . 

The  4  pounds  of  solid  matter  recovered  in  the 
butter,  which  contains  3.83  pounds  of  fat,  together 
with  the  salt  and  water  present,  make  about  4.6 
pounds  of  marketable  butter. 

From  96  to  98  per  cent  of  the  total  fat  of  the  milk 
is  recovered  in  the  butter.  About  three  times  more 
fat  is  lost  in  the  skim  milk  than  in  the  buttermilk. 
Nearly  90  per  cent  of  the  casein  and  albumin  and  85 
per  cent  of  the  milk  sugar  finds  its  way  into  the  skim 
milk.  The  buttermilk  is  composed  of  the  constituents 
present  in  the  cream,  minus  what  has  been  removed 
in  the  butter.  About  7  per  cent  of  the  ash  of  the 


THE  CHEMISTRY  OF  BUTTER  MAKING         69 

milk  goes  into  the  cream.  The  buttermilk  contains 
about  10  per  cent  of  the  original  casein  and  albumin 
and  about  15  per  cent  of  the  milk  sugar. 

69.  Composition  of  Butter.  —  Average  butter  con- 
tains about  10^  per  cent  of  water.  Some  samples 
may  contain  as  low  as  8  and  others  as  high  as  20 
per  cent.  An  excess  of  water  in  butter  should  be 
avoided,  as  it  unfavorably  influences  the  keeping 
qualities  and  affects  the  grain  and  other  desirable 
characteristics.  An  excess  of  water  is  due  either 
to  poor  methods  of  butter  making  or  to  intentional 
incorporation  of  water  to  increase  weight.  If  a 
butter  contains  too  small  an  amount  of  water,  as  8 
per  cent,  it  fails  to  have  the  best  physical  qualities. 
When  butter  is  overchurned  and  large  lumps  are 
formed,  greater  amounts  of  water  and  buttermilk 
are  retained  in  the  butter.  The  water  content  of 
butter  is  materially  affected  by  the  temperature  of 
churning,  washing,  and  working.  Whenever  the 
churning  is  done  at  a  high  temperature,  warm  wash 
waters  are  used  and  the  butter  is  worked  but  little, 
an  abnormal  amount  of  water  will  be  present ;  while 
butter  that  is  churned  at  a  low  temperature  and 
washed  with  not  too  cold  water  will  have  the  mini- 
mum water  content.  If,  however,  the  churning 
is  continued  in  not  too  cold  wash  water,  an  addi- 
tional but  not  excessive  amount  of  water  can  be 
incorporated  in  the  butter.  Rich  creams  also  have 
a  tendency  to  produce  butter  with  the  maximum 
water  content. 


70  DAIRY  CHEMISTRY 

The  casein  content  of  butter  ranges  from  one  half 
to  three  per  cent;  average  butter  usually  contains 
about  one  per  cent.  An  excess  of  casein  and  albu- 
min is  usually  found  in  poor  butters,  causing  them  to 
retain  a  large  amount  of  water  and  to  readily  undergo 
fermentation  changes.  The  ash  and  salt  content 
ranges  from  one  to  three  and  a  half  per  cent, 
average  butter  containing  about  two  and  a  quarter 
per  cent.  The  amount  of  fat  in  butter  ranges  from 
80  to  90  per  cent,  average  butter  containing  about 
85  per  cent.  The  fat  varies  with  the  water  content, 
those  butters  which  contain  the  most  water  contain 
the  least  fat,  and  butters  with  the  highest  fat  content 
contain  the  least  water.  There  is  only  a  general  re- 
lationship between  the  quality  of  the  butter  and  its 
percentage  content  of  water,  fat,  casein,  and  ash. 
Two  butters  may  have  the  same  percentage  of  these 
ingredients  and  be  widely  different  in  taste,  general 
physical  properties,  and  commercial  value. 

70.  Butter  Colors.  —  Normal  butter  has  a  charac- 
teristic yellow  color,  due  to  the  presence  in  milk  of 
a  distinctive  nitrogenous  coloring  material  called  by 
Blyth  lacto-chrome.  The  amount  of  this  coloring 
matter  is  influenced  by  the  food  consumed  and  by 
the  individuality  of  the  animal.  Milks  or  butters 
that  do  not  contain  this  natural  color  are  con- 
sidered abnormal,  and  in  order  to  impart  the  de- 
sired color  to  the  butter,  a  very  small  amount  of 
butter  color  is  used.  Most  of  the  butter  colors  are 
made  from  harmless  materials.  Occasionally,  how- 


THE  CHEMISTRY  OF  BUTTER   MAKING          71 

ever,  objectionable  coloring  substances  are  used,  par- 
ticularly those  made  from  the  coal-tar  dyes.  Some  of 
the  butter  colors  are  made  from  the  seed  of  the  Bixa 
orellana.  The  use  of  harmless  butter  colors  has  not 
been  regarded  by  courts  as  adulteration  of  butter. 

71.  Overruns.  —  One  pound  of  butter  fat  will  make 
about  one  and  one  sixth  pounds  of  butter.  During 
the  process  of  butter  making,  the  slight  loss  of  fat 
in  the  skim  milk  and  buttermilk  is  more  than  com- 
pensated for  by  the  added  water,  casein,  and  salt 
in  the  butter.  The  additional  butter  made  from 
a  pound  of  butter  fat  is  called  the  overrun ;  that 
is,  the  extent  to  which  the  churn  overruns  the 
test.  The  amount  of  overrun  depends  upon  the 
completeness  of  skimming,  thoroughness  of  churn- 
ing, and  the  way  in  which  the  butter  is  handled. 
In  some  cases,  the  overrun  amounts  to  .1  of  a 
pound  per  pound  of  butter  fat,  and  in  some  cases 
to  nearly  .2  of  a  pound.  The  method  in  most 
common  use  for  calculating  the  butter  yield  from 
the  fat  content  of  milk  is  to  increase  the  weight 
of  the  butter  fat  by  one  sixth.  This  factor  is  the 
one  most  used,  and  was  adopted  by  the  Association 
of  Agricultural  Colleges  and  Experiment  Stations 
as  the  factor  for  converting  butter  fat  into  butter. 
A  butter  maker  can  readily  determine  the  amount  of 
overrun  by  dividing  the  total  number  of  pounds 
of  butter  produced  for  a  given  time  by  the  number 
of  pounds  of  fat  in  the  milk  delivered  to  the  cream- 
ery during  that  period.  In  case  the  overrun  amounts 


72  DAIRY  CHEMISTRY 

to  only  .1,  the  butter  maker  can  conclude  that  errors 
in  the  manipulation  of  the  test  or  excessive  losses  in 
skimming  and  butter  making  have  occurred.  While, 
on  the  other  hand,  excessive  gains  in  overrun  are  also 
due  to  errors  in  manipulation. 

72.  Dividends.  —  Since  the  value  of  milk  for  butter- 
making  purposes  is  directly  proportional  to  its  fat 
content,  it  follows  that  the  amount  of  fat  in  the 
milk,  as  determined  by  the  Babcock  test,  can  be 
taken  as  the  basis  for  making  out  dividends  in 
creameries.  The  usual  method  followed  is,  first,  to 
determine  the  total  number  of  pounds  of  fat  deliv- 
ered by  each  patron  ;  this  is  done  by  multiplying 
the  total  number  of  pounds  of  milk  by  the  percentage 
of  fat  as  obtained  from  the  composite  test.  The  total 
number  of  pounds  of  fat  delivered  to  the  creamery 
by  all  of  the  patrons  is.  then  determined.  The  ex- 
penses of  manufacture,  including  the  sinking  fund, 
are  deducted  from  the  proceeds  of  the  sales.  These 
expenses  depend  upon  the  amount  of  butter  manu- 
factured, the  amount  of  money  reserved  for  the 
sinking  fund,  and  all  other  necessary  expenses 
incurred  in  the  manufacture  and  sale  of  the  butter. 
The  cost  of  manufacture  usually  varies  from  2|  to 
4  cents  per  pound  for  butter.  The  cost  of  manu- 
facture is  deducted  from  the  gross  receipts  and 
then  the  price  per  pound  of  the  butter  fat  is 
determined.  From  the  price  per  pound  of  the 
butter  fat  (not  butter)  the  dividend  of  each  patron 
is  calculated. 


THE  CHEMISTRY  OF  GUTTER  MAKING 


73 


EXAMPLE.     Five  patrons  deliver  to  the  creamery  dif 
ferent  amounts  of  milk  which  test  as  follows :  — 


PATRON 

POUNDS  MILK 

FAT  FOUND  BY  TEST 

1 

1512 

4.0 

2 

1700 

3.6 

3 

1200 

4.8 

4 

2100 

3.4 

5 

1400 

4.5 

From  this  milk  365  pounds  of  butter  are  made;  the 
butter  is  sold  for  21  cents,  and  3  cents  is  deducted  for 
cost  of  manufacture  and  sinking  fund.  The  dividends 
are  made  out  in  the  following  way :  — 


LB.  FAT 

1512  x  .040  =  60.48 

1700  x  .036  =  61.20 

1200  x  .048  =  57.60 

2100  x  .034  =  71.40 

1400  x. 045=  63.00 


60.48  x. 2094  =  $12.66 
61.20  x  .2094  =  12.82 
57.60  x. 2094=  12.06 
71 . 40  x. 2094=  14.95 
63.00  x, 2094=  13.19 


Total  313.68 

3651b.  x  18  X  =$65.70. 
$65.70  -h  313.7  =  $.2094. 


73.  Judging  Butter.  —  Butter  is  judged  on  the  basis 
of  flavor,  texture,  color,  taste,  and  finish.  If  butter 
is  unsound  or  abnormal  in  any  way,  it  is  apparent 
in  the  general  physical  properties.  In  order  to 
accurately  judge  butter,  a  person  must  cultivate  the 


74  DAIRY  CHEMISTRY 

senses  of  taste  and  smell  so  as  to  detect  any  objec- 
tionable flavors  or  odors,  and  the  extent  to  which  a 
butter  may  vary  from  a  perfect  sample.  The  scale 
of  points  usually  assigned  in  butter  judging  are  as 
follows :  — 

Flavor    <     e 45      Salt 10 

Texture 25      Finish 5 

Color 15 


CHAPTER  VIII 

THE   SANITARY  CONDITION   OF  MILK 

74.  Unwholesome  Milk.  —  By  the  sanitary  condi- 
tion of  milk  is  meant  its  condition  as  to  wholesome- 
ness  for  either  food  purposes  direct  or  for  manufac- 
ture into  butter  or  cheese.      Milks  that  are  in  the 
best  sanitary  condition  are  also  those  most  suitable 
for  butter  and  cheese  making ;  milk  that  is  not  suit- 
able for  food  should  not  be  used  for  dairy  purposes. 
Milks  are  most  frequently  unsound  because  of  dis- 
eased  conditions  of   the  animals  or  because  of   the 
presence  of  dirt  and  filth  of  various  descriptions  due 
to  lack  of  care  of  the  animals  or  of  the  dairy  utensils. 
The  spread  of  contagious  diseases  is  often  due  to 
unsound    milk,     where    disease    germs    find    lodg- 
ment,   readily   undergo   propagation,  and   are    then 
disseminated. 

75.  Factors  influencing  the  Sanitary  Condition  of 
Milk.  —  The   factors   which    influence   the   sanitary 
condition  or  wholesomeness  of  milk  are :  — 

1.  Condition  of  the  animals  as  to  health. 

2.  Care  of  the  animals. 

3.  Care  of  the  milk  and  dairy  utensils. 

4.  Food  and  water  which  the  animals  receive. 

75 


76  DAIRY  CHEMISTRY 

Unsanitary  condition  of  milk  may  be  due  to  one 
or  more  of  these  or  to  other  factors,  the  most  fre- 
quent causes  of  contamination  being  lack  of  care  of 
the  animals,  the  milk,  and  the  dairy  utensils. 

Condition  of  the  Animals  as  to  Health.  —  A  diseased 
animal,  as  one  suffering  from  advanced  stages  of 
tuberculosis  or  from  other  disease,  does  not  give 
sound  or  wholesome  milk.  The  variations  in  the 
composition  of  the  milk  when  cows  are  suffering 
with  disease  are  often  slight,  scarcely  sufficient  to 
change  the  percentage  composition  of  the  fat,  casein, 
and  albumin.  A  careful  examination  of  the  milk, 
however,  will  usually  show  the  presence  of  abnormal 
bodies,  products,  of  the  disease  germ  many  of  which 
are  toxic  in  character.  Milk  should  be  fairly  con- 
stant in  composition  from  day  to  day.  When  the 
fat  content  is  found  to  vary  between  wide  limits,  it 
is  frequently  due  to  a  diseased  condition  of  the  ani- 
mal. Normal  health  is  followed  by  fairly  constant 
composition  of  milk ;  limited  variations  are  to  be 
expected,  but  not  wide  ones.  Sound  health  of  the 
animals  is  the  first  requisite  in  securing  a  milk  sup- 
ply of  high  sanitary  condition.  In  some  forms  of 
disease,  the  milk  will  show  the  presence  of  an  abnor- 
mal amount  of  urea,  a  white  crystalline  compound 
formed  from  disintegration  of  the  muscular  tissues 
of  the  body  which  have  failed  to  be  excreted  and 
carried  off  by  the  kidneys.  In  normal  milk,  this 
compound  is  present  to  the  extent  of  .001  per  cent, 
but  in  diseased  milk  it  is  frequently  present  in  much 


THE  SANITARY  CONDITION  OF  MILK  77 

larger  amounts.  Other  compounds  in  diseased  milk 
are  albuminous  substances  known  as  toxins,  which  are 
products  of  various  disease  germs.  These  toxins  are 
poisonous  in  their  action  and  are  sometimes  more 
injurious  than  the  disease  germ  itself.  In  the  case 
of  milk  from  tuberculous  animals,  a  small  amount  of 
toxic  material  is  present.  Woll,  in  his  translation  of 
Grotenfelt's  work,  "  The  Principles  of  Modern  Dairy 
Practice,"  says  that  in  the  earlier  stages  of  tuber- 
culosis the  milk  often  has  an  abnormal  yellowish 
tinge. 

The  condition  of  the  animals  as  to  health  is  directly 
dependent  upon  the  care  they  receive  and  the  sanitary 
surroundings  in  barns,  stables,  and  fields. 

Care  of  the  Animals.  —  When  cows  are  kept  in 
crowded  and  unclean  stables  with  but  little  fresh  air, 
sanitary  milk  cannot  be  expected.  When  under  such 
conditions  for  any  length  of  time,  the  animals  be- 
come unhealthy,  and  even  where  they  themselves 
are  not  diseased,  the  milk  as  soon  as  drawn  absorbs 
the  unclean  atmosphere  of  the  stable,  which  readily 
renders  it  unsound.  Lack  of  cleanliness  in  the  sta- 
bles and  in  the  care  of  the  animals  is  one  of  the  most 
frequent  causes  of  unsound  milk.  The  liquid  and 
solid  excrements  of  the  stable  are  teeming  with 
various  ferment  bodies,  the  air  is  filled  with  dust 
particles  which  contain  ferments  and  fermentable 
substances,  and  as  soon  as  the  milk  is  drawn  it  is 
contaminated.  In  order  to  keep  the  stables  in  a 
wholesome  condition,  a  liberal  amount  of  bedding 


78  DAIRY  CHEMISTRY 

and  absorbents  should  be  used.  In  localities  where 
straw  cannot  be  procured,  sawdust,  shavings,  peat, 
and  other  materials  are  employed.  In  addition,  a 
small  amount  of  land  plaster,  or  gypsum,  will  be 
found  valuable  for  the  purpose  of  deodorizing  the 
stable.  Gypsum  is  used  at  the  rate  of  about  half  a 
pound  per  day  for  each  animal  and  is  sprinkled  in 
the  stalls  and  trenches.  Lime  in  any  other  form 
than  the  sulphate  is  not  suitable  for  use  in  the  stable. 
Instead  of  absorbing  the  odors,  quicklime  and  slaked 
lime  decompose  the  refuse  materials,  causing  more 
odors  to  be  produced.  Lime  sulphate,  or  land  plaster, 
can  usually  be  procured  at  about  15.00  per  ton,  and 
is  a  valuable  fertilizer ;  when  added  to  the  manure 
it  increases  its  value  by  preventing  unnecessary  fer- 
mentation and  loss  of  ammonia.  Some  deodorizing 
materials  and  so-called  disinfectants  simply  mask  the 
odors  of  the  stable  without  disinfecting  them.  Not 
only  the  stables,  but  often  filthy  yards  and  fields,  are 
direct  causes  of  pollution  of  milk,  and  some  of  the 
diseases  to  which  milk  is  subject  are  due  to  contami- 
nation from  the  soil.  Where  a  large  amount  of 
manure  is  banked  against  the  stable,  the  air  which 
diffuses  through  the  walls  is  contaminated.  Un- 
drained  pasture  lands  are  often  a  cause  of  trouble, 
and  occasionally  the  output  of  a  creamery  or  cheese 
factory  is  lessened  in  value  because  of  such  contami- 
nation. Numerous  cases  of  this  character  are  on 
record.  Mr.  Willard,  a  pioneer  American  cheese- 
factory  man,  found  that  the  production  of  a  poor 


THE  SANITARY  CONDITION  OF  MILK          79 

quality  of  cheese  was  due  to  the  milk  obtained  from 
one  herd.  Whenever  the  milk  from  this  herd  was 
omitted,  good  cheese  was  produced,  and  when  the 
milk  was  added,  a  poor  quality  was  obtained.  An 
examination  of  the  surroundings  of  the  herd  which 
caused  the  trouble  showed  that  the  cows  in  passing 
to  and  from  the  milking  shed  walked  through  a 
marshy  place  covered  with  green  pond  scum  and 
other  decomposing  materials,  particles  of  which  ad- 
hered to  the  udders,  dried,  and  then  fell  into  the 
milk  pails  during  milking,  and  fouled  the  milk.  In 
the  care  of  animals,  the  importance  of  an  abundance 
of  sunlight  cannot  be  overestimated.  Many  disease 
germs  are  destroyed  by  the  action  of  strong  sunlight. 
Strong  sunlight  and  pure  air  are  the  best  disinfec- 
tants, and  in  many  stables  there  is  a  great  lack  of 
both .  Experiments  made  with  growing  animals  show 
that  there  is  a  decided  difference  in  general  health 
and  vigor  between  those  reared  in  dark  and  light 
stables.  When  the  stable  is  not  properly  ventilated, 
the  carbon  dioxid  thrown  off  by  the  lungs  as  respira- 
tion products  unites  with  the  ammonia  formed  by  the 
decay  of  the  manure  and  produces  ammonium  car- 
bonate, which  is  often  deposited  in  the  form  of  a 
white  coating  upon  the  stones  and  beams  of  the 
stable.  This  shows  that  the  stable  is  poorly  venti- 
lated. Ammonium  carbonate  is  an  irritating  alka- 
line compound,  and  when  present  in  excessive  amounts 
has  a  destructive  action  upon  mucous  membranes. 
It  is  this  material  which  collects  upon  carriage  tops 


80  DAIRY  CE1EM1STRY 

and  harnesses  stored  in  poorly  ventilated  stables.  As 
is  well  known,  it  causes  rotting  of  the  leather,  and 
as  could  be  reasonably  assumed  has  a  similar  destruc- 
tive action  upon  the  mucous  membranes.  Animals 
can  stand  a  low  temperature  in  pure  air  with  less 
discomfort  than  a  higher  temperature  with  impure 
air.  However,  good  ventilation  does  not  necessarily 
mean  cold  stables.  Stables  can  be  so  constructed 
that  the  income  and  outgo  of  air  can  be  regulated, 
rather  than  leaving  the  ventilation  to  faulty  con- 
struction. Ventilators  made  of  drain  tiles  are  more 
sanitary  than  those  made  of  wood.  An  old  ventilat- 
ing flue  is  often  a  source  of  pollution,  due  to  the 
moist  air  causing  decay  of  the  wood,  which  then 
furnishes  lodgment  for  disease  germs.  In  order  to 
secure  the  best  sanitary  conditions  in  a  stable,  the 
walls  should  be  whitewashed  at  least  once  a  year, 
oftener  if  any  contagious  disease  has  occurred. 

Care  of  Milk  and  Dairy  Utensils.  —  Milk  is  often 
rendered  unsanitary  by  unnecessary  exposure  to  foul 
air,  and  by  handling  in  unclean  pails,  pans,  and  other 
dairy  utensils.  In  order  to  improve  the  keeping 
qualities  of  milk,  it  should  be  cooled  by  exposure  to 
clean,  pure  air.  When  not  cooled  at  once,  fermenta- 
tion changes  often  begin  immediately,  causing  an  in- 
crease in  the  bacterial  content  of  the  milk.  Too 
frequently  milk  is  strained  in  the  stable,  in  which 
case  it  becomes  additionally  fouled  from  the  stable 
air,  rilled  with  dust  particles  carrying  innumerable 
ferment  bodies.  The  straining  should  be  done  out- 


PLATE  III 


DIRT,   HAIR,    MANURE,    ETC.,    IN    CENTRIFUGAL    SLIME 
FROM   MILK 


THE  SANITARY  CONDITION  OF  MILK          81 

side  of  the  stable,  preferably  in  the  milk  room. 
Metal  strainers  composed  of  50  mesh  wire  gauze 
should  be  reenforced  by  clean  cloth  strainers  for 
the  removal  of  the  finer  dirt  particles.  Pressed  tin 
pails  which  do  not  have  seams  are  preferable  for 
dairy  use. 

In  washing  pails,  lukewarm  water  should  first  be 
used.  If  the  water  is  too  hot  the  albumin  of  the 
milk  is  coagulated,  forming  a  slime  over  the  surface 
of  the  utensil.  Albumin  is  coagulated  at  a  tem- 
perature of  about  160°  F.,  and  the  first  wash  water 
should  be  below  this  temperature.  The  lukewarm 
water  should  be  followed  by  a  thorough  washing 
with  hot  water  and  soap,  and  this  in  turn  by  boiling 
water,  or  preferably  live  steam,  so  that  there  will  be 
thorough  sterilizing.  The  dairy  utensils  should 
then  be  exposed  in  a  clean  place  to  bright  sunlight 
for  several  hours.  After  being  thoroughly  cleaned, 
the  utensils  are  sometimes  contaminated  by  dust  and 
dirt  particles  carried  by  the  wind.  Too  much  care 
cannot  be  bestowed  upon  the  cleaning  of  the  dairy 
utensils,  particularly  the  straining  cloths.  When 
milk  and  cream  are  delivered  at  the  factory  where 
live  steam  is  available,  the  factory  man  will  save 
himself  much  trouble  and  annoyance  by  thoroughly 
steaming  the  cans. 

Milk  rooms  are  often  kept  in  an  unclean  condi- 
tion, and  foul  odors  are  present  due  to  milk 
that  has  been  spilled  and  has  putrefied.  Particles 
of  the  dried  milk  containing  ferment  bodies  are 


82  DAIRY  CHEMISTRY 

given  off  from  unclean  floors,  sinks,  and  shelves,  and 
float  about  in  the  air  of  the  milk  room,  and  when 
fresh  milk  is  exposed  to  this  unclean  air  it  is  readily 
seeded  with  the  spores  of  any  ferment  bodies  that 
may  be  present  in  the  dust  particles.  As  an  exam- 
ple of  this,  Soxhlet  noted  that  when  milk  was  placed 
on  a  particular  shelf  in  the  milk  room  it  soon  became 
offensive  and  indicated  butric  acid  fermentation. 
An  examination  of  the  milk  rack  showed  that  at 
some  time  a  pan  of  milk  had  been  spilled  on  the 
shelf  above  the  one  causing  the  trouble.  The  lower 
side  of  the  shelf  had  not  been  thoroughly  cleaned, 
and  whenever  a  fresh  pan  of  milk  was  placed  on  the 
lower  shelf,  spores  or  seeds  fell  into  the  milk  and 
fouled  it. 

There  is  great  lack  of  care  in  the  commercial 
handling  and  shipping  of  milk.  It  is  often  unneces- 
sarily left  exposed  at  small  stations,  and  the  cans  are 
frequently  reshipped  without  cleaning. 

Food  and  Water  which  the  Animal  Receives.  —  The 
nature  of  the  food  which  the  animal  receives  influ- 
ences the  sanitary  condition  of  the  milk  to  a  some- 
what less  extent  than  the  other  factors  enumerated. 
Scant  or  abnormal  amounts  of  food,  or  foods  of 
unusual  composition,  may  unfavorably  affect  the 
sanitary  condition  of  the  milk.  The  relation  of 
the  food  to  the  composition  and  quality  of  the  milk 
is  discussed  in  another  chapter  of  this  work.  Some 
foods,  as  rape,  turnips,  and  rye  fodder  at  the  head- 
ing-out stage,  impart  an  undesirable  taste  to  milk, 


THE   SANITARY  CONDITION   OF  MILK  83 

This  is  due  to  the  presence  of  essential  oils  and  other 
noxious  compounds  which  pass  directly  into  the  milk 
without  chemical  change.  Milk  of  the  highest  sani- 
tary value  is  obtained  when  the  animals  are  properly 
fed  and  the  food  reasonably  conforms  to  a  balanced 
ration.  Abnormal  milk  will  result  from  feeding  one 
material  to  excess.  Whenever  cows  are  fed  on  a 
mixed  ration,  consisting  of  two  or  three  grains, 
coarse  fodders  not  overripe,  and  a  small  amount  of 
roots  or  silage,  the  quality  of  the  milk  from  a  sani- 
tary point  of  view,  provided  all  other  conditions  are 
satisfactory,  is  all  that  could  be  desired. 

The  purity  of  the  water  supply  is  a  very  impor- 
tant factor  in  the  production  of  sanitary  milk. 
Impure  drinking  water  is  often  the  cause  of  un- 
wholesome milk.  Surface  water  collected  in  stag- 
nant pools  is  unsuitable  for  animals  to  drink,  for 
although  it  may  not  produce  a  diseased  condition 
of  the  animals,  it  will  either  directly  or  indirectly 
affect  the  quality  of  the  milk.  No  animal  can  do 
its  best  work  in  milk  production  if  compelled  to 
drink  impure  water. 

None  but  pure  water  should  be  used  for  cleansing 
milk  utensils.  Numerous  cases  of  typhoid  fever  are 
recorded  which  were  due  to  milk  pails  and  cans 
being  washed  in  impure  water  and  the  typhus  bacilli 
thus  gaining  access  to  the  milk. 

76.  Colostrum  Milk.  —  The  milk  given  by  a  cow 
for  the  first  three  or  four  days  after  calving  is  quite 
different  in  color,  taste,  and  appearance  from  milk  in 


84  DAIRY  CHEMISTRY 

its  normal  condition.  Such  milk  is  called  colostrum 
milk,  and  has  a  different  chemical  composition  from 
ordinary  milk.  Colostrum  milk  is  yellow  in  color 
and  has  a  sweetish  taste  and  a  characteristic  oily 
feeling.  When  boiled  it  coagulates  on  account  of 
the  large  amount  of  albumin  which  is  present. 
When  hot  water  is  poured  into  colostrum  milk,  it 
curdles.  Colostrum  milk  has  a  higher  specific  grav- 
ity than  normal  milk,  frequently  reaching  1.064. 

COMPOSITION  OF  COLOSTRUM  MiLK1 

PER  CENT 

Water 71.50 

Solids 28.50 

Solids  contain  :  — • 

Fat 6.04 

Casein 3.50 

Albumin 12.67 

Sugar 4.85 

Ash 1.35 

Undetermined 0.09 

28.50 

The  term  "  colostrum  "  is  used  because  of  the  presence 
in  such  milk  of  circular  bodies  larger  than  the  fat 
globules,  and  known  as  colostrum  cells.  These  co- 
lostrum cells  are  similar  in  structure  to  the  white 
corpuscles  in  blood,  from  which  it  is  supposed  they 
are  derived.  When  examined  under  the  microscope 
while  the  milk  is  still  warm,  they  show  the  amoeboid 
movement  of  the  white  corpuscles. 

1  Analysis  made  by  the  author. 


PLATE   IV 


COLOSTRUM    MILK 


THE  SANITARY   CONDITION   OF  MILK          85 

The  colostrum  cells  begin  to  make  their  appear- 
ance in  the  milk  about  a  week  before  the  calf  is 
born.  Four  or  five  days  after  calving  the  albumin 
decreases  and  the  milk  gradually  reaches  its  normal 
condition.  The  colostrum  acts  as  a  purge  upon  the 
young  calf. 

The  creaming  of  colostrum  milk  is  very  imperfect 
on  account  of  the  albumin  present  in  such  large 
quantities.  Colostrum  milk  should  never  be  mixed 
with  other  milk,  because  it  will  prevent  creaming  by 
the  gravity  process  and  it  clogs  the  separator.  Co- 
lostrum produces  an  inferior  butter  product,  and  in 
cheese  making  causes  trouble  as  it  seriously  inter- 
feres with  the  curing  and  keeping  qualities  of  the 
cheese.  Colostrum  is  not  as  objectionable,  for  sani- 
tary reasons,  as  it  is  on  account  of  affecting  the 
quality  of  the  dairy  products. 

77.  Tyrotoxicon  is  a  poisonous  chemical  compound 
found  in  stale  milk  and  old  cheese.  It  is  produced 
by  bacteria,  and  is  a  ptomaine  or  poisonous  nitrog- 
enous body  formed  from  decomposing  albuminous 
matter.  When  separated  and  examined  with  the 
microscope,  the  tyrotoxicon  appears  in  long,  needle- 
shaped  crystals.  When  present  in  milk  in  small 
quantities  it  produces  diarrhosa  and  symptoms  simi- 
lar to  those  of  cholera.  It  proves  fatal  when  in- 
jected into  the  veins  of  small  animals.  The 
tyrotoxicon  is  sometimes  developed  in  ice  cream 
made  and  handled  in  unclean  ways.  Inasmuch  as 
tyrotoxicon  is  produced  by  bacteria  which  feed  upon 


86  DAIRY  CHEMISTRY 

decomposing  products,  the  utmost  cleanliness  should 
be  practiced  in  order  to  prevent  its  formation. 

78.  Fibrin  in  Milk.  —  Another  nitrogenous  com- 
pound in  milk  is  fibrin,  which  is  also  present  in  blood 
and  forms  the  "  clot."     The  best  proof  of  the  presence 
of  fibrin  in  milk  is  the  microscopic  appearance  of  the 
fat  globules.      As  previously  stated,  the  fat  globules 
always  appear  in  little  groups  or  colonies.     It  is  sup- 
posed that  they  are  held  together  by  bands  or  meshes 
of    fibrin  which  tend    to   prevent    their    coming  to 
the  surface  in  the  gravity  creaming  process.     The 
fibrin  in  milk  is  about  the  same  in  amount  as  the 
urea.     Fibrin  is  produced  by  the  action  of  the  fibrin 
ferment.     The  chemical  tests  for  its  determination 
in  milk  are  unsatisfactory. 

79.  Gases   in  Milk.  —  The  gases  which    are    dis- 
solved in  the  milk  as  it  comes  from  the  cow  are  : 
nitrogen,  oxygen,  and   a    small    amount  of    carbon 
dioxide.      Nitrogen  and  oxygen    are  found    in  the 
milk  in  about  the  same  proportion  as  in  pure  spring 
water.      As  milk  gets  older,   the  oxygen  decreases 
and  the  carbon  dioxide  increases.     Carbon  dioxide 
is  the  gas  which  is  given  off  in  respired  air  ;  in  stale 
milk  the  oxygen  has  been  used  up  to  form  carbon 
dioxide.     At  the  end  of  four  or  five  days,  90  per 
cent  of  the  gas  in  milk  is  carbon  dioxide.     There  is 
always  more  gas  in  old  than  in   fresh  milk.     When 
the    milk   becomes  saturated  with    gas,    the  gas  is 
given  off  ;  and  as  it  escapes  from  the  surface  of  cream 
or  thick  milk,  it  leaves  small  holes  on  the  surface. 


THE  SANITARY  CONDITION  OF  MILK          87 

In  addition  to  carbon  dioxide,  other  gases  of  a  dif- 
ferent character  may  be  present  in  milk  and  in 
cheese  making  cause  the  curd  to  float  :  such  as 
hydrogen,  which  is  given  off  in  butyric  acid  fermen- 
tation, and  derivatives  of  the  marsh-gas  series  of 
gases.  The  gases  in  milk  are  a  part  of  the  products 
formed  by  bacteria,  and  impure  milk  when  made 
into  dairy  products  may  cause  trouble,  not  only 
from  the  gases  present,  but  also  from  subsequent 
action  of  the  bacteria. 

80.  The  Keeping  Qualities  of  Milk  are  directly 
proportional  to  its  germ  content.  Milks  that  have 
been  produced  from  healthy  animals  under  the  most 
sanitary  surroundings  will  contain  but  little  dirt 
and  foreign  matter  carrying  the  microorganisms 
which  produce  fermentation  changes.  Milks  which 
readily  become  sour  or  undergo  fermentation  are  un- 
suitable for  food  purposes,  as  they  indicate  previous 
contamination  in  some  way.  For  infant  feeding  the 
wholesomeness  or  sanitary  condition  of  milk  is  of 
more  importance  than  its  fat  content. 

The  microscope  is  frequently  employed  to  deter- 
mine the  presence  of  dirt  and  foreign  materials  in 
milk.  A  microscopic  examination  of  the  milk  supply 
of  large  cities  shows  that  there  is  much  to  be  desired 
in  the  way  of  a  better  quality  of  milk  for  general 
food  purposes.  The  health  of  the  consumer  is  jeop- 
ardized by  continued  use  of  impure  milk. 


CHAPTER    IX 

THE  CHEMISTRY  OF  CHEESE  MAKING 

81.  Cheese  Making  and  Butter  Making  Compared.  — 
In  butter  making  the  object  is  to  secure  as  much  as 
possible  of  the  milk  fat  in  the  form  of  butter.     In 
cheese  making  the  casein  as  well  as  the  fat  must  be 
recovered.    In  butter  making,  fermentation  processes 
are  employed  for  ripening  the  cream  so  as  to  secure 
more  exhaustive  churning  and  to  produce  a  better 
quality  of  butter  ;  in  cheese  making,  also,  ferments 
are  employed  for  the  production  of  acid  to  coagulate 
the  milk  and  to  produce    desirable  flavors   in    the 
cheese.     In  cheese  making  the  ferments  take  a  more 
extended  part  than  in  butter  making.     The  funda- 
mental principles  of  cheese  making  are  best  under- 
stood by  first  considering  the  general  properties  of 
the  milk  proteids,  particularly  casein  and  albumin. 

82.  Proteids  of  Milk.  —  Milk  contains  a  number 
of    proteid    or    nitrogenous    compounds,  as    casein, 
albumin,  and  derivative  products,  as  albumoses  and 
peptoses.      The  nitrogenous  compounds  or  proteids 
differ  in  composition  from  the  sugars  and  fats  by 
containing  the  element  nitrogen  in  addition  to  the 
carbon,  hydrogen,  and  oxygen  that  are  present  in  the 
sugars  and    fats.      The  principal  proteids  of  milk, 


THE  CHEMISTRY  OF  CHEESE  MAKING         89 

casein  and  albumin,  are  alike  in  general  composition, 
but  differ  materially  in  their  physical  properties. 
The  proteids  are  the  compounds  to  which  special 
attention  is  given  in  human  and  animal  nutrition,  for 
they  impart  characteristic  value  to  foods  and  perform 
functional  processes  which  other  nutrients  are  not 
capable  of  doing.  The  reader  is  referred  to  works  on 
nutrition  and  the  feeding  of  animals  for  the  func- 
tions of  protein  and  its  value  as  a  nutrient.  The 
milk  proteids,  particularly  casein,  undergo  numerous 
changes  during  cheese  making,  and  the  process  con- 
cerns itself  largely  with  the  correct  handling  of  these 
compounds. 

83.  Casein.  —  In  fresh  milk  the  casein  is  in  nearly 
a  soluble  condition  and  is  one  of  the  solids  of  the 
milk  serum.     With  the  formation  of  lactic  acid,  the 
casein  is  changed  from  a  semi-soluble  to  an  insoluble 
condition,  and  the  lactic  acid  unites  with  the  casein, 
forming  a   new  and   insoluble    compound.      When 
sufficient  acid  is  developed,  the  precipitation  of  the 
casein  is  complete.     This  is  commonly  spoken  of  as 
curdling  of  the  milk.     The  addition  of  dilute  acids 
to  fresh  milk  will  produce  the  same  result,  coagu- 
lation, and  in  cheese  making  the  object  of  the  fer- 
ment action  is  to  produce  acid  to  change  the  casein 
from  a  soluble  to  an  insoluble  condition.      Dilute 
acids    do    not    coagulate    or   precipitate    the    milk 
albumin. 

84.  Albumin.  —  When  milk  is  allowed  to  sour  and 
curdle,  it  separates  into  a  coagulated  mass  containing 


90  DAIRY  CHEMISTRY 

the  casein  and  fat,  and  whey  which  contains  the  albu- 
min and  milk  sugar.  If  the  clear  whey  is  heated, 
a  yellowish  white,  flakelike  substance  is  formed. 
This  is  coagulated  albumin.  The  albumin  in  milk 
is  coagulated  at  temperatures  ranging  from  157°  to 
161°  F.,  but  in  the  ordinary  processes  of  cheese 
making  the  temperatures  reached  are  not  suffi- 
ciently high  for  the  coagulation  of  the  albumin, 
and  as  a  result  it  remains  in  the  whey.  If  higher 
temperatures  were  attempted,  excessive  losses  of 
fats  would  occur,  the  casein  would  be  unfavor- 
ably affected,  and  a  poor  quality  of  cheese  would 
be  produced.  The  chief  distinctions  between  ca- 
sein and  albumin  are  that  albumin  is  coagulated 
by  heat,  while  casein  is  not,  and  casein  is  coagu- 
lated by  dilute  acids,  but  the  albumin  is  not  pre- 
cipitated. 

85.  Rennet.  —  In  order  to  control  the  process  of 
fermentation  and  the  coagulation  of  the  milk,  ren- 
net is  used.  Rennet  is  an  extract  prepared  from 
the  mucous  membrane  or  lining  of  the  fourth  stomach 
of  the  calf.  It  contains  various  ferment  bodies,  as 
lactic  and  peptic  ferments,  which  are  the  chief  agents 
in  bringing  about  the  changes  necessary  for  the  di- 
gestion of  milk.  When  rennet  is  added  to  ripened 
milk,  it  produces  the  same  effect  as  the  addition  of 
dilute  acid.  A  temperature  of  from  86°  to  90°  is 
favorable  for  the  action  of  the  rennet  ferments. 
Prior  to  the  addition  of  the  rennet,  the  milk  is 
ripened  with  a  starter,  as  in  the  ripening  of  cream. 


THE  CHEMISTRY  OF  CHEESE  MAKING          91 

It  would  be  possible  for  cheese  to  be  made  by  allow- 
ing the  milk  to  sour  by  natural  processes,  but  under 
such  conditions  a  poor  quality  of  cheese  is  produced, 
for  the  process  of  fermentation  Cannot  then  be  con- 
trolled as  when  a  starter  is  used  for  ripening  the 
milk  and  rennet  for  coagulating  it.  The  chief 
action  of  rennet  in  cheese  making  is  to  coagulate 
the  milk.  In  the  ripening  of  the  cheese,  the  rennet 
appears  to  act  secondary  to  the  enzymes  or  soluble 
ferments  which  are  normally  present  in  all  milk. 

86.  The  Rennet  Test.  — The  rennet  test  is  employed 
in  cheese  making  to  determine  when  the  milk  is  in 
the  right  condition  for  adding  the  rennet.  The 
rennet  test  is  made  in  the  following  way  :  5  cc. 
of  rennet  extract  is  diluted  and  mixed  in  a  flask 
with  45  cc.  of  water,  140  cc.  of  milk  from  the 
vat  is  placed  in  a  small  cup,  5  cc.  of  the  diluted 
rennet  solution  added  and  thoroughly  stirred,  and 
the  time  required  for  the  complete  coagulation  of 
the  milk  noted.  In  making  the  test,  a  knife  is 
used  to  determine  when  the  coagulation  is  com- 
pleted. If  more  than  sixty  seconds  are  required 
for  coagulation,  the  milk  is  not  sufficiently  ripened 
for  the  addition  of  the  rennet.  For  ordinary  pur- 
poses of  Cheddar  cheese  making,  the  milk  is  suffi- 
ciently ripened  when  it  coagulates  in-  from  45  to  55 
seconds.  If  the  milk  coagulates  in  less  than  40 
seconds,  it  is  overripe  and  requires  different  manipu- 
lations for  cheese-making  purposes.  The  ripeness 
of  the  milk,  as  shown  by  the  rennet  test,  materially 


92  DAIRY  CHEMISTRY 

influences  the  way  in  which  the  curd  ripens  in  the 
vat ;  the  rennet  test  also  serves  as  a  guide  in  subse- 
quent manipulations. 

87.  Process  of  Cheddar  Cheese  Making.  —  In  order 
to  more  intelligently  discuss  the  principal  changes 
that  take  place  in  cheese  making,  the  details 
of  the  process  of  Cheddar  cheese  making  are 
here  briefly  given  :  When  the  milk  is  received  at 
the  factory,  it  is  weighed  and  its  general  condition 
as  to  purity  noted/  A  small  sample  is  retained 
for  testing  with  the  Babcock  test,  as  in  creamery 
work.  Any  foul  or  unsound  milk  is  rejected  as 
unsuitable  for  cheese-making  purposes.  The  mixed 
milk  is  then  warmed  in  the  vat  by  means  of  steam 
or  otherwise  until  a  temperature  of  86°  to  88°  F.  is 
reached.  The  milk  is  heated  gradually,  and  is 
stirred  to  prevent  the  separation  of  the  fat.  The 
starter  is  added,  and  when  the  proper  degree  of 
ripeness  is  thought  to  have  been  reached  the  rennet 
test  is  applied.  If  the  milk  is  found  to  be  in  suit- 
able condition,  the  rennet  is  then  added  at  the  rate 
of  3  to  5  ounces  per  thousand  pounds  of  milk.  If 
the  milk  contains  a  high  percentage  of  fat,  the 
maximum  amount  of  rennet  is  added  at  the  higher 
temperature.  Ordinarily,  however,  the  quantity  of 
rennet  required  and  the  temperature  of  the  milk 
when  it  is  added  vary  with  the  season  of  the  year, 
the  condition  or  individuality  of  the  milk,  and  the 
kind  of  cheese  desired  to  produce.  These  are  factors 
that  must  be  thoroughly  understood  by  the  cheese 


THE  CHEMISTRY  OF  CHEESE  MAKING 


maker,  and  the  process  of  making  adapted  to  exist- 
ing conditions.  After  the  rennet  has  been  added  and 
thoroughly  mixed,  about  twenty  minutes  are  allowed 
for  complete  coagulation  of  the  milk.  The  time  of 
coagulation,  however,  will  vary  with  the  conditions 
stated.  When  the  curd  is  in  a  state  where  .  it 
readily  "  breaks "  and  maintains  its  form,  it  is  cut 
with  a  curd  knife  into  small  cubes.  After  cutting, 
the  mass  is  gently  agitated  for  about  five  minutes  so 
as  to  secure  hardening  of  the  curd  particles  and  to 
prevent  mechanical 
losses  of  fat.  This 
agitation  also  pre- 
vents the  curd  from 
matting  and  forming 
large  masses.  The 
temperature  of  the 
vat  is  then  raised 
gradually  at  the  rate 
of  two  degrees  for  every  five  minutes  until  a  tem- 
perature of  102°  F.  is  reached.  The  stirring  is 
continued  at  intervals  to  prevent  the  curd  parti- 
cles from  matting.  The  heating  of  the  curd  brings 
about  a  number  of  important  changes  and  results  in 
contraction  of  the  curd  and  more  complete  expulsion 
of  the  whey.  The  changes  brought  about  by  the  di- 
gestive ferments  present  in  the  rennet  and  the  milk 
cause  a  softening  of  the  curd.  The  ripeness  of  the 
curd  in  the  vat  is  determined  by  the  hot-iron  test. 
This  test  is  made  in  the  following  way :  A  piece  of 


FIG.  17.  —  Cheese  vat. 


94  DAIRY  CHEMISTRY 

cheese  is  pressed  against  a  hot  iron  and  immediately 
withdrawn.  The  length  of  the  threads  adhering  to 
the  iron  are  proportional  to  the  degree  of  ripeness 
of  the  curd.  If  the  threads  are  an  eighth  of  an 
inch  long,  the  curd  is  usually  in  a  sufficiently  advanced 
stage  for  the  removal  of  the  whey.  In  case  a  quick- 
curing  cheese  is  desired,  threads  of  greater  length 
should  be  shown.  After  the  whey  is  removed,  the 
curd  is  allowed  to  pack  and  form  large  masses  in  the 
bottom  of  the  vat.  These  masses  are  cut  into  blocks 
and  placed  in  a  pile  so  as  to  undergo  further  diges- 
tion changes  and  develop  acid.  The  curd  is  ground 
when  the  threads  shown  by  the  hot-iron  test  are  a 
fourth  of  an  inch  or  more.  The  grinding  and  subse- 
quent salting  of  the  curd  retard  the  fermentation 
process.  Before  grinding,  the  curd  is  kept  at  a 
temperature  of  90°  to  95°;  after  grinding  and  salt- 
ing, the  temperature  is  reduced  to  about  80°  F. 
The  matting  of  the  curd  particles  is  spoken  of 
as  cheddaring.  The  ground  and  salted  curd  is 
placed  in  molds  and  pressed  in  the  cheese  press. 
A  gradual  and  uniform  pressure  is  maintained  for 
about  24  hours.  The  cheese  is  then  ready  for 
the  curing  room.  As  in  the  case  of  butter  making, 
exact  details  for  the  manipulation  of  all  kinds  of 
milk  cannot  be  given.  The  general  principles  of 
cheese  making,  however,  should  be  thoroughly  under- 
stood, and  then  the  processes  may  be  varied  to  meet 
different  conditions  arising  in  the  manufacture  of 
different  kinds  of  milk  into  cheese. 


THE  CHEMISTRY  OF  CHEESE  MAKING         95 

In  the  manufacture  of  cheese  a  record  should  be 
kept  of  the  time  required  for  the  different  opera- 
tions. The  following  points  should  be  noted  :  — 

Condition  of  milk. 

Pounds  of  milk  in  vat. 

Per  cent  of  fat  in  milk. 

Rennet  test  for  ripeness. 

Temperature  of  milk  when  set. 

Amount  of  rennet  used. 

Rate  of  rennet  per  1000  pounds  of  milk. 

Time  cut. 

Minutes  in  curdling. 

Time  heat  is  applied. 

Time  required  to  raise  to  102°. 

Hot-iron  test  when  dipped. 

Time  dipped. 

Time  from  cutting  to  dipping. 

Pounds  of  whey. 

Per  cent  of  fat  in  whey. 

Time  ground. 

Hot-iron  test  when  ground. 

Time  salted. 

Amount  of  salt  in  curd. 

Rate  of  salt  per  1000  pounds  of  milk. 

Time  put  to  press. 

Time  pressed. 

Weight  of  green  cheese. 

Weight  of  milk  per  pound  of  cheese. 

Weight  of  milk  per  pound  of  cured  cheese. 

Remarks. 


96  DAIRY  CHEMISTRY 

88.  Process  of  Stirred  Curd  Cheese  Making.  —  In 

cheddar  cheese  making,  the  curd  is  allowed  to  mat 
in  the  vat  after  the  whey  has  been  removed.  In  the 
stirred  curd  process,  the  curd  is  not  allowed  to  mat 
or  cheddar,  it  is  kept  stirred  and  manipulated  in 
such  a  way  that  the  whey  is  drained  off  and  the  curd 
particles  are  not  allowed  to  unite.  It  is  then  salted, 
pressed,  and  cured.  By  this  process  of  cheese  mak- 
ing, a  softer  and  milder-flavored  cheese  is  produced. 
This  stirred  curd  process  results  in  the  incorporation 
of  a  larger  amount  of  water  in  the  cheese,  and  the 
ripening  requires  less  time  than  for  cheddar  cheese. 
These  two  processes,  the  cheddar  and  stirred  curd, 
are  often  so  varied  that  a  sharp  dividing  line 
between  the  two  cannot  be  made.  For  firm,  long- 
keeping  export  cheese  the  cheddar  process  is  fol- 
lowed, and  for  a  soft,  mild,  quick-ripening  cheese 
the  stirred  curd  process  is  employed. 

89.  Distribution  of   Milk  Solids  in  Cheese  Mak- 
ing.—  About  one  half  of  the  milk  solids  are  recov- 
ered in  the  cheese.     The  fat  is  not  as  completely 
recovered  as  in  butter  making.     The  whey  usually 
contains  about  5  per  cent  of  the  total  fat  of  the  milk. 
Of  the  12^  or  13  pounds  of  solid  matter  in  milk, 
about  3  pounds  of  the  casein,  3^  pounds  of  the  fat, 
and  a  portion  of  the  ash  are  recovered  in  the  green 
cheese,  while  the  milk  sugar,  albumin,  and  a  portion 
of  the  ash  are  lost  in  the  whey.     The  solid  matter 
of  cheese  is  mainly  composed  of  fat  and  casein,  and 
any  increase  in    the  amount  of  fat  in  the  milk  is 


THE  CHEMISTRY  OF  CHEESE  MAKING          97 

followed  by  a  corresponding  increase  in  the  fat  con- 
tent of  the  cheese.  It  was  formerly  believed  that 
milk  of  high  fat  content  could  not  be  economically 
made  into  cheese  and  that  only  a  certain  percent- 
age of  the  fat  in  milk  could  be  recovered  in  cheese 
making.  Experiments  have  shown  this  idea  to  have 
been  incorrect. 

90.  Curing  of  Cheese.  —  New  cheese  is  lacking  in 
flavor  and  digestibility.  By  allowing  the  cheese  to 
undergo  the  ripening  or  curing  process,  desirable 
flavors  are  developed,  and  the  casein  is  changed  into 
a  more  soluble  and  easily  digested  form.  The  cheese 
was  formerly  placed  in  a  curing  room  at  a  tempera- 
ture of  65°  to  70°.  The  curing  room  was  kept  at  an 
even  temperature  and  the  moisture  content  of  the  air 
controlled  as  far  as  possible.  During  recent  years, 
however,  there  has  been  a  tendency  to  cure  cheese  at 
a  lower  temperature.  At  one  time  it  was  believed 
that  the  rennet  used  in  making  cheese  was  the  chief 
agent  in  ripening  or  curing,  and  it  was  held  that  a 
temperature  of  from  65°  to  70°  F.  was  the  most  suit- 
able for  the  action  of  the  rennet  ferments.  Investi- 
gations by  Babcock,  Russell,  Van  Slyke,  and  others 
have  shown  that  the  soluble  ferments  or  enzymes, 
which  are  normal  products  of  all  normal  milk,  can 
be  utilized  as  the  chief  factors  in  the  ripening  of 
cheese,  and  that  it  is  possible  to  ripen  cheese  inde- 
pendent of  the  rennet  ferments. 

There  are  two  classes  of  ferments  —  the  organized 
or  insoluble  ferments,  and  the  soluble  or  chemical 


98  DAIRY  CHEMISTRY 

ferments  which  are  also  called  enzymes.  The  in- 
soluble or  organized  ferments  are  mainly  bacterial 
bodies  of  definite  form  and  structure  propagated 
from  a  spore  or  seed.  These  organized  ferments 
develop  in  milk,  meat,  or  any  other  suitable  mate- 
rial if  conditions  as  to  temperature  and  moisture  are 
favorable.  The  chemical  ferments,  or  enzymes,  are 
products  of  living  organisms  capable  of  producing 
ferment  changes.  Chemical  ferments  cannot  be 
seen  with  the  microscope  ;  they  are  simply  chemical 
substances  capable  of  inducing  fermentation  changes 
without  entering  into  the  composition  of  the  material 
or  giving  up  any  of  their  own  substance  to  the  re- 
acting bodies.  Milk  contains  a  tryptic-like  ferment 
or  enzyme,  which  peptonizes  the  casein  and  other 
proteids,  forming  proteoses  and  other  soluble  bodies. 
In  the  curing  of  cheese,  it  has  been  found  that  the 
ripening  process  can  be  carried  on  entirely  by  these 
soluble  ferments  and  at  a  lower  temperature  than 
required  by  the  organized  ferments  or  bacteria.  The 
process  of  cheese  curing  at  a  low  temperature  is  akin 
to  the  curing  of  meat  in  cold  storage. 

Experiments  on  a  commercial  scale  have  shown 
that  cheese  can  be  cured  at  a  temperature  of  less 
than  50°  F.,  resulting  in  the  production  of  a  better 
quality  of  cheese,  less  shrinkage  in  weight,  and  less 
loss  of  solid  matter  than  by  curing  at  a  high  tem- 
perature. As  a  result,  the  cold  curing  of  cheese  has 
gradually  replaced  the  old  process  of  high  tempera- 
ture curing.  This  is  an  advantage  also  in  that  less 


THE  CHEMISTRY  OF  CHEESE  MAKING         99 

loss  occurs  from  cheese  becoming  unsound  during 
the  curing  process,  and  larger  yields  of  cured  cheese 
are  obtained  from  a  given  amount  of  milk.  In  the 
cold  curing  of  cheese  the  fermentation  changes  are 
brought  about  entirely  by  the  action  of  the  soluble 
ferments  or  enzymes  of  the  milk.  It  is  mainly  a 
digestion  process,  the  changes  taking  place  being 
similar  to  those  which  occur  in  the  first  stages  of 
the  digestion  of  the  proteids  in  the  stomach.  The 
acids  produced  unite  with  the  casein,  forming  more 
soluble  and  digestible  products.  Van  Slyke,  in  his 
studies  on  cheese  making,  states  that  lactic  acid 
forms  with  casein  two  compounds,  paracasein  and 
paracasein  monolactate,  which  contains  half  as  much 
acid  as  paracasein. 

Since  both  the  insoluble  or  organized  ferments  and 
the  enzymes  of  milk  take  an  important  part  in  the 
manufacture  and  curing  of  the  product,  it  is  highly 
important  that  the  milk  be  handled  in  the  most 
cleanly  way  possible,  so  as  to  reduce  the  germ  con- 
tent of  the  milk  and  prevent  the  formation  of  objec- 
tionable flavors  and  products  in  the  cured  cheese. 
Attention  should  be  given  to  the  sanitary  condition 
and  surroundings  of  both  the  creamery  and  cheese 
factory,  as  any  unsanitary  condition  may  affect  the 
quality  of  the  product. 

91.  The  Cheese  Yield  of  Milk. — Since  the  per- 
centage of  casein  to  fat  varies  in  different  milks,  it 
follows  that  the  cheese  yield  of  milk  is  not  directly 
proportional  to  its  fat  content.  Milks  of  the  high- 


100 


DAIRY  CHEMISTRY 


est  percentage  of  fat  are  not  proportionally  richer  in 
casein  than  milks  of  low  fat  content.  When  milk 
tests  3^  per  cent  fat,  100  pounds  will  make  about 
9.35  pounds  of  cheese.  One  pound  of  milk  fat  will 
make  from  2.6  to  2.7  pounds  of  cured  cheese.  The 
relation  of  the  fat  content  of  milk  to  its  cheese  yield, 
as  found  by  Babcock  at  a  number  of  Wisconsin 
factories,  is  as  follows  :  — 


No.  OF 
GKOUPB 

No.  OF 
REPORTS 

RANGE  OF  FAT 
PEE  CENT 

AVERAGE 

1'KI!    (KNT 

OF  FAT 

AVERAGE  YIELD 

<>1-  (.'IIF.F.SE  PER 
100  LH.  MILK 

LBS.  OF  CURED 
CHEESE  FOR 
1  LB.  FAT 

1 

24 

Under  3.25 

3.126 

9.194 

2.941 

2 

90 

3.25-3.50 

3.382 

9.285 

2.730 

3 

134 

3.50-3.75 

3.600 

9.407 

2.613 

4 

43 

3.75-4.00 

3.839 

9.806 

2.562 

5 

46 

4.00-4.25 

4.090 

10.300 

2.512 

6 

20 

Over  4.25 

4.447 

10.707 

2.407 

groups  347 

3.64 

9.566 

2.628 

92.  Testing  Cheese  by  the  Babcock  Milk  Test  — 
The  percentage  of  fat  in  cheese  can  be  determined 
by  the  Babcock  milk  test  in  the  following  way: 
With  a  sharp  knife  and  in  a  cool  room  cut  the 
cheese  into  small  pieces  about  the  size  of  wheat 
grains.  Weigh  into  a  test  bottle  5  gm.  of  this 
cheese  sample,  add  about  15  cc.  of  hot  water,  and 
shake  well  so  as  to  thoroughly  disintegrate  the 
cheese.  When  cool,  the  acid  is  added  and  the  test 
completed  in  the  usual  way.  The  reading  of  the 
test  bottle  is  multiplied  by  3.6  to  obtain  the  per  cent 


THE  CHEMISTRY  OF  CHEESE  MAKING       101 


of  fat  in  the  cheese.  This  is  because  the  test  bottles 
are  made  for  18  gm.  of  material  and  only  5  gm. 
of  cheese  were  used.  A  cheese  made  from  normal 
milk  should  contain  at  least  30  per  cent  fat,  and 
cheese  of  good  quality  shows  from  32  to  36  per  cent. 
93.  Composition  of  Cheese.  —  The  percentage  of 
fat  in  cheese  is  directly  proportional  to  the  richness 
of  the  milk  in  fat  and  the  amount  of  water  left  in 
the  cheese.  In  average  cheese  the  per  cent  of  fat 
always  exceeds  the  per  cent  of  casein.  This  is  be- 
cause the  milk  from  which  the  cheese  is  made  con- 
tains more  fat  than  casein.  Any  cheese  containing 
more  casein  than  fat  has  been  made  from  skim  milk. 
The  relation  of  the  composition  of  cheese  to  the  milk 
from  which  it  was  made  may  be  observed  from  the 
following  tables :  — 


COMPOSITION  OF  MII.K 

Water 

Fat 

Ash 

Casein  and 
Albumin 

Milk 
Sugar 

1.  Average  milk  .  .  . 
2.  4  per  cent  milk  .  .  . 
3.  Milk  with  cream  added 

87.52 
86.79 

85.87 

3.50 
4.00 
6.00 

0.80 

0.64 
0.77 

3.22 
3.71 
3.12 

4.80 

4.50 
4.13 

4.  Skim  milk  .... 

87.80 

2.75 

0.80 

3.95 

4.50 

COMPOSITION  OF  CHEESE 

Water 

Fat 

Casein  and 
Albumin 

34.29 
31.4 
32.43 
30.68 

33.76 
35.3 
43.55 
27.09 

27.47 

27.7 

20.00 
36.00 

3.  Milk  with  cream  added     .     .     . 

102  DAIRY  CHEMISTRY 

94.  Testing  Whey.  —  In  the  making  of  cheese  both 
the  whey  and  the  drippings  from  the  cheese  press 
should  be  frequently,  tested  for  fat,  so  as  to  deter- 
mine whether  there  has  been  any  unnecessary  loss. 
In  testing  whey,  the  special  bottles  made  for  testing 
skim  milk  may  be  used.     It  is  not  necessary  to  use 
17.6  cc.  of  acid,  because  the  casein  has  been  removed 
from  the  milk  and  the  acid  has  less  work  to  do. 
Use  about  8  cc.  of  acid. 

95.  Making  out  Dividends  in  Cheese  Factories.— 
The  dividends  in  cheese  factories  can  be  made  out 
on  the  basis  of  the  fat  content,  in  the  same  general 
way  as  described  in  section  72  for  making  out  divi- 
dends in  creameries.     The  fat  content  of  milk  is  a 
more  satisfactory  and  equitable  basis  for  making  out 
dividends  than  the  gross  weight  of  the  milk  regard- 
less of  its  composition.     As  previously  stated  (section 
91),  the  cheese  yield  of  milk  is  riot  always  propor- 
tional to  its  fat  content.     A  milk  testing  6  per  cent 
fat  will  not  make  twice  as  much  cheese  as  one  con- 
taining 3  per  cent  fat.     This  is  because  the  casein 
does  not  increase  proportionally  with  the  fat.     With 
average   milk,  however,  testing  from  3.4  to  4  per 
cent,  the  amount  of  cheese  that  can  be  made  is  prac- 
tically proportional  to  the  fat  content.     Inasmuch  as 
average  milk  usually  tests  between  these  amounts, 
the  fat  test  can  be  safely  used  as  the  basis  for  the 
making  out  of  dividends.     In  the  case  of  exception- 
ally rich  milk,  the  quality  of  the  cheese  is  materially 
increased  by  the  additional  fat.     Experiments  have 


THE  CHEMISTRY  OF  CHEESE  MAKING       103 

shown  that  the  value  of  the  cheese  is  almost  directly 
proportional  to  its  fat  content.  While  the  richer 
milks  make  a  smaller  quantity  of  cheese,  they  make 
cheese  of  higher  commercial  value,  and  hence  there 
is  no  injustice  in  paying  for  milks  for  cheese-making 
purposes  on  the  basis  of  the  fat  content.  Poor  milks 
make  a  slightly  larger  amount  but  a  poorer  quality 
of  cheese  than  the  richer  milks.  In  making  out 
dividends,  the  total  number  of  pounds  of  fat  deliv- 
ered by  each  patron  is  calculated  from  the  weight 
of  the  milk  and  its  percentage  of  fat.  The  cost  of 
manufacture  is  deducted  from  the  sales  and  the  price 
per  pound  of  the  milk  fat  sold  in  the  form  of  cheese 
determined,  and  then  the  amount  due  each  patron  is 
calculated  from  the  pounds  of  fat  due  him  and  its 
value  per  pound. 

96.  Comparative  Butter  and  Cheese  Returns  from 
Milk.  —  In  case  it  is  desired  to  compare  the  approxi- 
mate gross  income  from  the  same  amount  of  milk 
made  either  into  butter  or  cheese,  the  methods  for 
calculating  the  butter  yields  given  in  section  71  are 
used  for  determining  the  pounds  of  butter  produced 
from  a  given  quantity  of  milk  testing  a  certain  per- 
centage of  fat.  From  the  data  given  in  section  91, 
the  estimated  number  of  pounds  of  cheese  produced 
from  the  same  quantity  of  milk  can  also  be  calcu- 
lated. Comparisons  can  then  be  made  as  to  the 
gross  sales  from  either  the  butter  or  cheese  by  tak- 
ing the  average  market  price  of  each.  If  such  cal- 
culations are  made,  it  will  be  found  that  occasionally 


104  DAIRY  CHEMISTRY 

larger  proceeds  can  be  obtained  from  cheese  than 
from  butter,  and  then  again  the  sales  of  butter  will 
be  found  to  give  the  larger  returns.  In  determining 
the  net  income,  the  cost  of  production  and  the  com- 
parative value  of  the  by-products  must  also  be  con- 
sidered. Only  general  comparisons  can  be  made  as 
to  the  probable  income  from  the  manufacture  of 
butter  or  cheese.  As  to  the  relative  advantages  of 
butter  or  cheese  production,  much  depends  upon 
location,  markets,  and  general  conditions.  In  the 
general  average,  the  production  of  one  will  be  found 
to  be  about  as  profitable  as  the  other,  and  it  is  not 
advisable  to  make  frequent  changes. 

97.  Different  Kinds  of  Cheese.  —  By  varying  the 
process  of  cheese  making  so  as  to  cause  the  develop- 
ment of  specific  forms  of  fermentation,  different 
kinds  of  cheese,  as  Neufchatel,  Limburger,  Swiss, 
Edam,  Gouda,  and  Roquefort,  are  made. 

Neufchatel  is  a  soft  cheese,  made  from  sweet  milk 
by  adding  the  rennet  at  82°  F.  After  pressing,  it  is 
worked  and  kneaded,  and  then  put  up  in  packages 
and  covered  with  tinfoil. 

Limburger  is  a  variety  of  cheese  of  characteristic 
odor  and  flavor  resulting  from  special  ferment  action 
daring  the  curing  process. 

Stilton  cheese  is  a  soft,  rich  cheese  of  mild  flavor 
made  from  milk  to  which  cream  is  usually  added. 
For  the  curing  a  long  time  is  required  and  a  fungus 
with  bluish  green  threads  is  developed. 

Emmenthaler  or  Swiss  cheese  is  made  by  special 


THE  CHEMISTRY  OF  CHEESE  MAKING       105 

manipulation  and  direct  pressing  in  the  curd  presses. 
The  cheese  is  salted  from  the  outside  and  certain 
forms  of  fermentation  are  induced. 

Edam  is  a  hard,  dry  cheese,  usually  made  from  par- 
tially skimmed  milk  and  cured  by  a  slow  process  of 
fermentation. 

Gouda  is  somewhat  similar  to  Edam,  but  is  softer 
in  texture. 

Roquefort  is  a  soft  cheese  which  owes  its  char- 
acteristics to  special  forms  of  ferments  added  dur- 
ing the  process  of  manufacture.  When  ripened  a 
characteristic  mold  will  be  found  permeating  the 
cheese. 

A  number  of  special  brands  of  cheese,  put  up  in 
glass  and  porcelain  packages,  are  made  from  ordi- 
nary cheese  by  grinding  and  adding  fat,  usually  in 
the  form  of  butter.  The  sealed  package  is  then 
placed  in  cold  storage  so  as  to  allow  further  fer- 
mentation changes  to  take  place. 

Cottage  Cheese.  —  Cottage  cheese  can  be  prepared 
in  the  following  way  :  The  milk  is  first  allowed  to 
sour  and  is  then  heated  to  a  temperature  of  100°  F., 
or  the  coagulation  of  the  milk  can  be  completed,  if 
desired,  by  the  addition  of  hot  water,  temperature  of 
175°  F.,  at  the  rate  of  about  one  pint  per  gallon 
of  milk.  After  stirring  for  two  or  three  minutes, 
the  coagulated  mass  is  allowed  to  settle,  the  whey 
is  drawn  off  and  the  curd  collected  by  straining 
through  cheese  cloth.  If  the  milk  is  in  the  right 
condition  as  to  acidity,  a  fine,  soft-grained  curd  is 


106  DAIRY  CHEMISTRY 

secured.  Salt  is  added  as  desired,  and  the  palata- 
bility  and  food  value  are  increased  by  the  addition 
of  a  small  amount  of  cream  when  used.  Cottage 
cheese,  when  prepared  in  this  way,  has  a  high  food 
value. 


CHAPTER   X 

MILK  BY-PRODUCTS 

98.  Uses  of  By-products. —  In  the  manufacture  of 
butter  and  cheese  the  by-products    are  skim  milk, 
buttermilk,   and    whey.     These   products    are  used 
mainly  for  animal-feeding  purposes  and  have  a  high 
food  value.     Also  from  the  by-products  a  number 
of  commercial  articles  are  prepared.      From  whey, 
milk  sugar  is  manufactured,  and  from  skim  milk, 
proteids  are  precipitated  and  prepared  for  commer- 
cial uses. 

99.  Skim  Milk  —  Composition,  Value,  and  Use.  —  In 
the  manufacture  of  butter,  about  80  per  cent  of  skim 
milk  is   obtained.     The   chief  ingredients   of   skim 
milk  are  casein,  albumin,  ash,  and  milk  sugar.     Be- 
cause of  the  removal  of  the  fats  in  skimming,  the 
solids  not  fat  are  usually  present  in  the  skim   milk 
in    slightly  larger    proportions  than    in   the  whole 
milk.     Skim  milk  is  characterized  as  a  food  of  high 
proteid  content   and  it  is  valuable  in  combination 
with  other  foods    that  are  lacking  in  protein,  par- 
ticularly for  the  feeding  of  young  and  growing  ani- 
mals.    Average  skim  milk  contains  about  9.75  per 
cent  of  solid  matter,  of  which  3.7  pounds  are  casein 
and  albumin,  and  5.15  pounds  are  sugar,  the  remain  - 

107 


108  DAIRY  CHEMISTRY 

ing  .9  of  a  pound  being  principally  ash.  and  a  small 
amount  of  lactic  acid  and  other  compounds.  The 
principal  value  of  skim  milk  is  due  to  the  relatively 
large  amount  of  casein  and  albumin  it  contains,  over 
36  per  cent  of  the  solid  matter  being  in  these  forms. 
When  judiciously  used,  5  pounds  of  skim  milk 
will  produce  as  much  gain  in  the  feeding  of  young  pigs 
as  one  pound  of  farm  grains.  Professor  Henry,  of 
the  Wisconsin  Experiment  Station,  states  that  when 
corn  is  worth  28  cents  per  bushel,  skim  milk  has  a 
feeding  value  of  15  cents  per  hundred  pounds.  In 
order  to  secure  the  largest  returns  from  the  feeding 
of  skim  milk,  it  should  be  fed  with  grains  at  the  rate 
of  about  3  pounds  of  skim  milk  per  1  pound  of  grain. 
If  fed  in  larger  amounts  than  this,  smaller  returns 
are  secured  from  the  skim  milk.  When  the  nu- 
trients in  a  pound  of  grain  and  5  pounds  of  skim 
milk  are  compared,  it  will  be  found  that  5  pounds 
of  skim  milk  contain  less  total  nutrients  than  the 
pound  of  grain.  The  unique  value  of  skim  milk 
lies  in  the  fact  that  it  is  rich  in  protein  and  when 
combined  with  other  feed  makes  a  ration  more  pala- 
table and  also  increases  the  digestibility  of  the  feeds 
with  which  it  is  combined.  When  judiciously  used, 
skim  milk  is  valuable  not  only  for  the  nutrients  it 
contains,  but  also  because  of  making  the  nutrients 
of  the  grains  and  foods  with  which  it  is  combined 
more  digestible  and  valuable  to  the  body.  Skim 
milk  should  be  fed  preferably  when  sweet.  When 
partially  soured  it  may  cause  digestion  disorders,  due 


MILK  BY-PRODUCTS  109 

to  the  presence  of  various  ferment  bodies.  Skim 
milk  that  is  fully  soured  causes  less  digestion  trouble 
than  when  partially  soured. 

In  the  handling  of  skim  milk  the  greatest  care 
should  be  exercised  to  prevent  its  contamination  and 
abnormal  fermentation  from  taking  place.  The 
tyrotoxicon  organism  may  develop  in  skim  milk  and 
cause  cholera-like  symptoms.  The  separator  slime 
should  never  be  added  to  skim  milk,  as  it  contains  a 
large  proportion  of  the  dirt  of  the  milk.  Sheuerlen 
and  Bank  state  that  most  of  the  tubercle  bacilli  in 
milk  are  separated  in  the  slime  of  the  centrifugal. 

The  keeping  qualities  and  sanitary  condition  of 
skim  milk  are  improved  by  pasteurizing  or  sterilizing 
it  at  the  time  the  milk  is  separated.  If  the  skim 
milk  is  sterilized,  it  should  be  cooled  and  then  pro- 
tected from  further  inoculations.  Unless  it  is  prop- 
•  erly  cared  for,  the  sterilizing  may  have  but  little 
effect  in  improving  its  value.  Too  frequently  the 
factoryman  and  farmer  give  but  scant  attention  to 
the  care  of  the  skim  milk.  A  little  foul  sour  milk  is 
left  in  the  skim-milk  tank  from  day  to  day,  and  this, 
acting  as  a  starter,  immediately  sours  any  fresh  skim 
milk  which  is  added.  Some  diseases,  as  hog  cholera, 
have  been  spread  through  lack  of  care  in  handling 
the  skim  milk  at  the  creamery. 

Separator  skim  milk  differs  but  little  in  composi- 
tion from  skim  milk  obtained  by  the  gravity  pro- 
cess. From  the  separator  skim  milk  the  fat  has 
been  quite  thoroughly  removed,  while  that  obtained 


110  DAIRY  CHEMISTRY 

by  the  gravity  process  contains  a  larger  amount  of 
fat.  Experiments  have  shown  that  the  additional 
fat  in  the  gravity  skim  milk  produces  only  small 
additional  gains  over  separator  skim  milk,  the  gains 
being  of  less  importance  than  the  commercial  value 
of  the  butter  fat.  Skim  milk  should  not  be  stored 
or  handled  in  rusty  iron  pails  or  cans,  because  the 
small  amount  of  acid  present  has  a  solvent  action 
upon  metals,  and  if  too  much  iron  zinc  or  tin  is  dis- 
solved in  the  milk,  it  has  an  injurious  effect  when  fed 
to  animals.  The  handling  of  skim  milk,  buttermilk, 
and  whey  in  unclean  ways  is  frequently  the  cause 
of  abnormal  fermentation  and  the  contamination  of 
dairy  products. 

100.  Whey — Composition,  Value,  and  Use.  — Whey 
differs  in  composition  from  skim  milk  by  containing 
less  solid  matter  because  of  the  removal  of  the  casein 
in  cheese  making.  Average  whey  contains  about  7  per 
cent  of  solid  matter,  the  larger  portion  of  which  is 
milk  sugar,  5.2  per  cent.  It  also  contains  the  albumin 
of  the  milk,  which,  as  previously  stated,  is  not  retained 
in  the  cheese.  There  is  less  ash  in  whey  than  in  skim 
milk,  due  to  a  portion  of  the  mineral  matter  combining 
with  the  casein  and  being  recovered  in  the  cheese. 

While  whey  contains  less  solid  matter  and  proteids 
than  skim  milk,  it  nevertheless  has  a  material  feed- 
ing value.  Experiments  have  shown  that  two 
pounds  of  whey  are  about  equal  in  feeding  value  to 
one  pound  of  skim  milk.  In  general,  ten  pounds  of 
whey  will  produce  as  much  gain  in  live  weight  of 


MILK  BY-PRODUCTS 


111 


growing  animals  as  one  pound  of  farm  grains.  In 
the  handling,  care,  and  use  of  whey,  the  same  general 
statements  made  in  regard  to  skim  milk  will  apply. 

101.  Fertilizer  Value  of  Milk  By-products.  —  When 
butter  is  sold  from  the  farm,  there  is  very  little  fer- 
tility lost  in  the  form  of  the  principal  plant  food  ele- 
ments,—  nitrogen,  phosphorus,  and  potassium.     The 
butter  fats  are  composed  of  the  three  elements,  car- 
bon, hydrogen,  and  oxygen.     The  nitrogen  and  the 
ash  or  mineral  elements  are  present  in  the  skim  milk 
and  buttermilk,  and  hence  when  butter  is  sold  there 
is  practically  no  fertility  lost.     When  cheese  is  sold, 
part  of  the  fertility  is  lost  in  the  form  of  nitrogen, 
which  is  present  in  the  casein.     In  dairy  farming, 
the  crop-producing  power  of  the  soil  is  not  lessened, 
provided  the  farm  manure  is  judiciously  cared  for 
and  used. 

102.  Comparative   Value   of  Cow's   Milk  and  the 
Milk  of  Other  Domestic  Animals.  —  In  order  to  com- 
pare the  general   feeding   value  of  cow's  milk  and 
skim  milk  with  the  milk  of  other  domestic  animals, 
the  following  table  is  given  :  — 


WATER 

FAT 

SUGAR 

ASH 

CASEIN  AND 
ALBUMIN 

Mare's  milk      .... 

88.49 

2.86 

4.75 

0.55 

3.35 

Sow's  milk  

84.00 

4.60 

3.15 

1.05 

7.25 

Sheep's  milk    .... 

82.25 

5.30 

4.35 

1.00 

7.10 

Skim  milk  

90.25 

0.10 

5.15 

0.80 

3.70 

Cow's  milk  

87.00 

4.00 

5.00 

0.75 

3.25 

CHAPTER   XI 

THE  ADULTERATION   OF   DAIRY  PRODUCTS 

103.  Oleomargarine. — Oleomargarine  and  butterine 
are  butter  substitutes  made  from  animal  fats,  cotton- 
seed oil,  and  other  materials,  and  resemble  butter  in 
composition  and  taste.    They  contain  about  the  same 
percentage  of  water,  fat,  salt,  and  nitrogenous  matter 
as  butter,  but  differ  in  not  containing  butyrin  and 
other  characteristic  volatile  fatty  acids  present  in  but- 
ter and  not  in  butter  substitutes.     In  the  manufac- 
ture of  oleomargarine,  the  beef  fats  are  put  through 
filter  presses  to  remove  a  portion  of  the  hard  fats, 
which  are  used  for  the  manufacture  of  candles  and 
soap.      The    softer   fats,    with    cotton-seed   oil,    are 
placed    in   churns   together   with   sweet   milk,    and 
churned,  salted,  and  worked  like  butter.     By  varying 
the  proportion  of  hard  and  soft  fats,  different  grades 
of  oleomargarine  can  be  produced,  and  these  are  sold 
under   various    trade   names.      These   products   are 
readily  detected  upon  chemical  analysis,  as  they  fail 
to  yield  the  requisite  amount  of  volatile  fatty  acids 
(see  section  40). 

104.  Simple  Methods  for  detecting  Oleomargarine. — 
The  boiling  or  spoon  test  is  made  in  the  following 
way:    A  small  piece  of  the  sample  is  melted  in  a 

112 


THE  ADULTERATION  OF  DAIRY  PRODUCTS     113 

large  spoon  with  gentle  heat.  The  process  is  has- 
tened by  stirring.  The  heat  is  then  increased,  the 
material  is  brought  to  the  boiling  point  and 
thoroughly  stirred.  Oleomargarine  and  renovated 
butter  boil  with  much  sputtering  and  produce  no 
foam,  or  very  little,  while  genuine  butter  in  boiling 
produces  more  foam  and  less  noise.  The  Water- 
house  test  is  conducted  in  the  following  way:  "Into 
a  small  beaker  pour  50  cc.  of  sweet  milk.  Heat 
nearly  to  boiling  and  add  from  5  to  10  gm.  of  butter 
or  oleomargarine.  Stir  with  a  glass  rod  until  the 
fat  is  melted.  The  beaker  is  then  placed  in  cold 
water  and  the  milk  stirred  until  the  temperature 
falls  sufficiently  for  the  fat  to  congeal.  At  this 
point  the  fat,  if  oleomargarine,  can  easily  be  collected 
into  one  lump  by  means  of  the  rod,  while  if  butter 
it  will  granulate  and  cannot  be  collected." 

105.  Renovated  Butter. — Low  grade  and  rancid 
butters  are  sometimes  subjected  to  the  process  known 
as  renovation.  The  butter  is  melted  and  poured 
into  cold  water,  so  as  to  recrystallize  the  fat  and 
remove  those  products  which  impart  the  undesirable 
flavors  and  odors.  The  butter  fats  are  then  re- 
worked and  salted,  and  the  product  is  ready  for  the 
market.  It  is  often  sold  as  fresh  butter.  Renovated 
butter  has  poor  keeping  qualities,  and  so  preserva- 
tives, as  boric  acid,  are  frequently  added  to  prevent 
the  fats  from  becoming  rancid.  When  melted  and 
recrystallized,  the  butter  fats  fail  to  form  crystals 
of  the  same  character  as  the  original  butter,  which 


114  DAIRY  CHEMISTRY 

enables  the  renovated  butter  to  be  easily  detected. 
Some  of  the  states  have  laws  requiring  that  butter 
treated  in  this  way  shall  be  stamped  or  labeled 
"Renovated  Butter." 

106.  Adulteration  of  Cheese.  —  Cheese  is  adulter- 
ated (1)  by  removing  a  portion  of  the  fat  from  the 
milk  and  then  manufacturing  the  skimmed  or  par- 
tially skimmed  milk  into  cheese ;   (2)  by  completely 
removing  the  milk  fats  and  substituting  other  and 
cheaper  fats,  thus  producing  so-called  "  filled  cheese." 
The   foreign   fats   are   incorporated  with    the   skim 
milk   while   in   the   vats   and   then   the   process   of 
cheese  making  is   completed,  with  slight   modifica- 
tions, as  outlined  in  the  chapter  on  Cheese  Making. 
The  addition  of   foreign  fats  to   the  cheese  can  be 
readily  detected  by  chemical  analysis,  as  cotton-seed 
oil  and  other  fats  have  different  chemical  and  physi- 
cal properties  from  butter  fats.     For  the  determina- 
tion of  the  per  cent  of  fat  in  cheese  by  the  Babcock 
test,    see  section  92.     Cheese  with  28   per  cent   or 
less  of  fat  can  be  considered  as  made  from  partially 
skimmed  milk,  and  the  lower  the  per  cent  of  fat  in 
the  cheese,  the  more  extensively  has  the  skimming 
been  practiced. 

107.  Adulteration   of   Milk.  —  The  way  in   which 
the   lactometer  and  Babcock  test  may  be  used   for 
detecting   skimming   and  watering   is   described   in 
Chapter  IV.     In  addition  to   skimming  and  water- 
ing, milk  is   sometimes  adulterated  by  the  addition 
of  preservatives.     The  materials  employed  for   the 


THE  ADULTERATION   OF  DAIRY  PRODUCTS     115 

preservation  of  milk  are  principally  borax,  boric  acid, 
formalin,  and  salicylic  acid.  Medical  authorities 
object  to  the  use  of  preservatives  in  dairy  prod- 
ucts and  other  foods  because  they  interfere  with  the 
normal  process  of  digestion.  Then,  too,  when  milk 
is  preserved  with  chemicals,  there  is  a  tendency  to 
practice  unclean  methods  in  its  handling,  and  less 
care  generally  is  taken  of  the  milk.  Abnormal 
amounts  of  preservatives  have  been  found  added  to 
market  milk  to  prevent  its  becoming  sour.  The 
producer,  the  wholesale  milk  dealer,  and  the  retailer 
each  adding  a  small  amount  make  in  the  aggregate 
an  abnormal  and  objectionable  quantity  of  preserva- 
tives, which  may  have  an  unfavorable  action  upon 
the  human  body.  In  the  creamery  and  cheese  fac- 
tory, the  addition  of  formalin  and  other  preservatives 
prevents  the  normal  ripening  of  milk  and  results  in 
the  production  of  butter  and  cheese  of  poor  quality. 
Not  only  from  a  sanitary  but  also  from  a  financial 
point  of  view,  preservatives  are  objectionable  and 
should  not  be  used  in  the  dairy.  Various  trade 
names  have  been  applied  to  the  different  preserva- 
tives, but  they  are  almost  invariably  composed  of 
borax,  boric  acid,  formalin,  or  salicylic  acid. 

In  addition  to  the  Babcock  test,  a  number  of  other 
methods  have  been  proposed  and  are  occasionally 
used  for  the  testing  of  milk  and  detecting  any  adul- 
terations. Many  of  these  methods  give  accurate  re- 
sults, but  they  require  more  skill  on  the  part  of  the 
operator,  are  more  expensive,  and  require  more  time 


116  DAIRY  CHEMISTRY 

than  the  Babcock  test,  and  hence  are  used  but  little. 
Some  of  the  methods,  as  the  Pioscope  and  the  Lacto- 
scope,  do  not  give  accurate  results. 

The  Beimling  method  is  quite  similar  to  the  Bab- 
cock  test,  a  centrifugal  being  used.  The  test  bottles, 
however,  are  smaller,  and  two  acids  instead  of  one 
are  employed.  Amyl  alcohol  is  required,  and  this  is 
apt  to  be  impure  and  cause  too  high  results. 

The  Lactocrite  method  has  been  in  use  in  Ger- 
many and  Denmark  for  some  time.  The  separation 
of  the  fat  is  made  by  means  of  acetic  and  sulphuric 
acids,  combined  with  centrifugal  action.  In  its 
workings  the  Lactocrite  is  quite  like  the  Babcock 
test.  The  centrifugal  used  is  in  form  like  the  Alpha 
separator.  The  method  gives  reliable  results.  It  is 
patented  and  the  apparatus  expensive. 

With  Gerber's  butyrometer  test,  the  fat  is  sepa- 
rated by  centrifugal  action  aided  by  sulphuric  acid 
and  amyl  alcohol.  This  method  combines  the  more 
important  features  of  the  Babcock  and  the  Beimling 
methods.  It  gives  accurate  results  and  is  quite 
extensively  used  in  Europe. 

Short's  Method.  —  In  this  test  an  alkali  solution  is 
first  added  to  the  milk,  which  changes  the  fat  into 
soap ;  the  soap  is  then  converted  into  insoluble  fatty 
acids  by  adding  sulphuric  acid,  and  the  fatty  acids 
are  measured  in  a  graduated  tube.  The  test  bottles 
are  similar  to  those  used  in  the  Babcock  test. 

In  Cochrane's  method  the  fat  is  separated  by  the 
combined  use  of  sulphuric  and  acetic  acids  and 


THE  ADULTERATION   OF  DAIRY  PRODUCTS     117 

ether.  The  fat  is  then  raised  into  a  graduated  tube, 
where  it  is  measured.  The  Cochrane  fat  bottles  are 
made  with  two  tubes,  one  for  measuring  the  fat  and 
the  other  for  adding  the  reagents. 

In  Failyer  and  Willard's  method  an  acid  first  is 
added  to  the  milk,  and  then  gasoline  to  collect  the 
fat.  The  gasoline  is  removed  by  a  current  of  air, 
and  the  fat  is  collected  in  the  graduated  neck  of 
the  test  bottle  and  measured. 

The  Lactoscope  and  Feser's  Pioscope  were  quite 
extensively  used  at  one  time.  They  are  optical 
methods  and  depend  upon  the  opacity  of  the  milk 
serum.  Both  of  these  methods  are  totally  unreli- 
able, the  results  being  very  inaccurate. 

Most  of  these  short  methods  are  not  sufficiently 
accurate  for  scientific  work,  or  as  final  evidence  in 
court  in  case  of  adulteration. 

108.  Dairy  Laws.  —  Some  states  and  countries 
have  passed  laws  prohibiting  the  sale  of  adulterated 
dairy  products.  Congress  has  also  passed  a  national 
law  prohibiting  the  coloring  of  oleomargarine  to 
resemble  butter.  The  injury  which  results  from 
the  sale  of  oleomargarine  and  filled  cheese  is  due 
more  to  their  being  dishonest  competitors  than  to 
their  unwholesomeness.  They  are  frequently  sold 
for  butter  and  cheese,  and  since  they  are  made 
to  resemble  them,  it  is  often  difficult  for  the  inex- 
perienced person  to  detect  the  adulterated  article. 
As  to  digestibility  and  food  value,  there  is  not  a 
great  difference  between  butter  and  oleomargarine. 


118  DAIRY  CHEMISTRY 

Experiments  have  shown  that  butter  is  slightly  more 
digestible  than  oleomargarine.  As  long  as  oleomar- 
garine is  sold  under  its  own  name,  there  is  little 
objection  to  its  use ;  but  people  naturally  prefer 
genuine  butter  and  cheese  to  imitation  articles,  and 
they  should  be  protected  in  securing  them.  It  is 
when  oleomargarine  is  sold  as  butter  that  the  prin- 
cipal injury  is  done  to  the  butter  industry.  For 
this  reason,  laws  have  been  passed  regulating  the 
sale  of  dairy  products  and  prohibiting  adulteration. 


CHAPTER   XII 

MARKET  MILK  AND   CREAM 

109.  Variable  Character  of  Market  Milk. —It  is 
estimated  that  one  third  of  the  milk  produced  in 
this  country  is  used  for  direct  consumption  by  the 
producer  or  is  sold  as  market  milk.  The  milk 
supply  of  large  cities  is  extremely  variable  in  char- 
acter, both  in  its  richness  in  fat  and  its  wholesome- 
ness  or  sanitary  condition.  In  those  states  where 
dairy  laws  have  been  enacted  and  the  laws  are 
reasonably  well  enforced,  milk  of  good  quality  is 
secured,  but  where  no  legal  control  is  exercised 
over  the  milk  supply,  it  is  often  of  very  poor  qual- 
ity. To  meet  the  requirements  of  the  consumer, 
milk  should  be  produced  from  animals  in  sound 
health,  and  the  milk  should  be  free  from  dirt,  have 
good  keeping  qualities,  and  contain  a  reasonable 
amount  of  fat.  In  order  to  supply  milk  of  the 
best  quality,  different  methods  of  handling  have 
been  devised,  the  most  satisfactory  and  cleanly 
way  being  to  supply  the  milk  in  sterilized  sealed 
bottles.  When  milk  is  conveyed  to  the  consumer 
in  this  form,  no  opportunity  presents  itself  for 
adulteration  or  for  the  milk  to  become  contami- 
nated by  unclean  methods  of  handling  or  through 
119 


120 


DAIRY  CHEMISTRY 


exposure  in  unclean  streets.  Usually  a  larger  price 
is  paid  for  milk  prepared  in  this  way.  The  sanitary 
condition  or  wholesomeness  of  the  milk  (see  Chap- 
ter VIII)  is  of  more  importance  than  its  fat  content. 
110.  Changes  in  Composition  of  Milk  during  Trans- 
portation. —  When  milk  is  transported  in  cans  and 
removed  with  a  long-handled  dipper,  it  changes  but 
little  in  composition  during  transportation,  the  agita- 
tion of  the  can  and  the  dipping  being  sufficient  to  pre- 
vent the  separation  of  cream.  This  question  has  been 
extensively  investigated  in  both  this  country  and 
Europe.  In  England,  one  of  the  large  dairy  firms 
supplying  milk  to  the  London  market  had  during 
the  season  a  number  of  thousands  of  samples  of 
milk  taken  from  the  wagons  at  different  points  on 
the  route  to  prevent  the  watering  of  the  milk  by 
the  drivers,  and  it  was  found  that  there  was  but 
little  change  in  the  solid  matter  of  the  milk.  Dur- 
ing one  season  over  11,000  samples  were  analyzed, 
with  the  following  results  :  — 


MILK 

CREAM 

Solid  Matter 

Solid  Matter 

1284 

483 

1288 

1099 

484 

At  the  Cornell  University  Experiment  Station  simi- 
lar results  were  obtained,  also  at  the  Canadian  Experi- 


MARKET  MILK  AND   CREAM  121 

ment  Station  at  Guelph.  The  excuse  sometimes 
offered  in  court  that  milk  has  lost  its  cream  while 
being  sold  is  not  valid,  as  all  the  experimental  evi- 
dence shows  that  when  milk  is  dipped  from  the  can 
with  a  long-handled  dipper  no  separation  of  the  fat 
takes  place.  While  milk  changes  in  its  per  cent  of 
solid  matter  but  little  during  transportation,  it  often 
becomes  sour  and  foul  through  unnecessary  exposure 
and  unclean  ways  of  handling. 

111.  Pasteurizing  Milk  and  Cream. — In  order  to 
prevent  milk  and  cream  from  readily  fermenting,  it 
is  sometimes  given  the  Pasteurizing  treatment.  This, 
consists  of  heating  the  milk  or  cream  to  a  tempera- 
ture of  159°  or  160°  F.  for  a  few  minutes  and  then 
cooling  and  protecting  it  from  further  inoculations. 
This  temperature  results  in  rendering  inactive  the 
greater  number  of  ferments  in  milk,  particularly 
those  of  an  objectionable  nature.  The  destruction 
of  the  ferment  bodies  prevents  rapid  souring  of  the 
milk,  especially  when  the  milk  is  protected  from 
further  contamination.  The  Pasteurizing  of  milk 
and  cream  is  usually  done  by  machinery,  the  milk 
being  agitated  so  as  to  secure  as  even  an  application 
of  temperature  as  possible.  The  longer  the  milk  is 
heated,  the  more  thorough  is  the  Pasteurizing  pro- 
cess. Not  all  of  the  germs  or  ferments  of  milk  are 
rendered  inactive  by  heating  to  a  temperature  of 
160°.  To  render  inactive  the  tuberculous  bacilli,  a 
temperature  of  180°  to  185°  is  required.  When  milk 
is  sterilized,  it  is  heated  to  a  higher  degree  than 


122  DAIRY  CHEMISTRY 

when  it  is  Pasteurized.  At  temperatures  above  185°, 
all  of  the  bacteria  are  destroyed  and  the  milk  is  ren- 
dered sterile.  When  milk  is  sterilized,  the  albumin 
is  coagulated ;  when  Pasteurized,  the  temperature  is 
not  sufficiently  high  to  coagulate  it.  The  Pasteuriz- 
ing of  milk  improves  its  sanitary  condition  and  often 
makes  an  unsound  milk  suitable  for  food  purposes. 
It  is  preferable,  however,  to  have  a  wholesome  and 
sound  milk  that  is  not  Pasteurized  rather  than  an 
unsound  milk  that  has  been  given  this  treatment. 
When  a  milk  is  Pasteurized,  its  germ  content  is 
reduced;  but  the  products  of  the  germs,  particu- 
larly the  toxins,  are  not  removed. 

The  Pasteurizing  of  cream  is  often  resorted  to  in 
making  butter.  When  the  cream  has  been  con- 
taminated in  any  way,  Pasteurizing  gives  good  re- 
sults. When  the  milk  has  been  produced  under 
the  most  sanitary  conditions,  Pasteurizing  is  less 
necessary.  The  preparation  and  sale  of  Pasteurized 
milk  and  cream  have  become  prominent  features  of 
the  milk  industry  in  a  number  of  cities.  For  home 
use,  milk  can  be  Pasteurized  in  the  following  way : 
glass  cans  are  thoroughly  cleansed  and  then  placed 
in  the  oven  so  as  to  become  sterilized.  When  par- 
tially cooled,  they  are  filled  with  fresh  milk  and  set 
in  water  at  a  temperature  of  about  162°.  After  being 
in  the  water  for  from  10  to  15  minutes,  with  the  tem- 
perature kept  at  160°,  the  cans  are  covered,  cooled, 
and  stored  at  a  low  temperature.  Not  all  milks  are 
suitable  for  food  even  when  Pasteurized.  Digestion 


MARKET  MILK  AND   CREAM  123 

experiments  indicate  that  perfectly  sound,  normal 
milk  is  more  completely  digested  than  either  Pas- 
teurized or  sterilized  milk ;  the  difference  in  diges- 
tibility, however,  between  sound,  fresh  milk  and 
Pasteurized  milk  is  small,  but  in  favor  of  the  fresh 
milk.  Sterilized  milk  is  less  digestible  than  Pas- 
teurized. 

112.  Condensed  Milk. — Another  method  of  pre- 
serving milk  is  to  remove  a  portion  of  the  water  by 
means  of  condensing  in  a  vacuum  pan  and  then  seal- 
ing the  condensed  product  while  hot.     Milk  that  is 
properly  condensed  can  be  kept  for  a  long  time,  and 
in  some  localities  it  is  the  main  source  of  milk  supply. 
Whenever  a  can  of  condensed  or  Pasteurized  milk  is 
opened,  the  same  care  is  necessary  to  protect  it  from 
contamination  as  if  it  were  fresh  milk. 

113.  Milk  as  Human  Food.  —  There  is  no  food  that 
has  a  higher  value  than  pure  milk.     Too  frequently 
its  nutritive  value  is  impaired  by  its  being  impure. 
Contaminated  milk,  like  any  impure  food,  should  not 
be  used.     Milk  should  form  a  part  of  the  dietary,  as 
it  is  easily  digested,  and  assists  in  rendering  other 
foods  more   digestible.     Experiments    have    shown 
that  at  average  prices  milk  is  not  a  luxury,  but  an 
economical  food.     Milk  furnishes  a  large  amount  of 
digestible  nutrients,  and,  in  the  case  of  a  number  of 
diseases,  it  is  the  only  food  that  should  be  allowed. 
Milks  with   either  the   maximum  or  minimum   fat 
content  are  not  the  best  for  food  purposes,  but  milk 
containing  about  4  per  cent  of  fat  generally  gives 


124  DAIRY  CHEMISTRY 

the  most  satisfactory  results  where  it  forms  a  large 
part  of  the  diet.  Milks  very  poor  or  very  rich  in 
fat  have  either  too  narrow  or  too  wide  a  nutritive 
ratio  (see  section  133),  while  normal  milk  is  a  well- 
balanced  food  containing  proteids,  carbohydrates, 
and  fats  in  the  right  proportions  for  supplying  the 
needs  of  the  body. 


CHAPTER  XIII 

INFLUENCE  OF  DIFFERENT  FOODS  UPON   THE   QUALITY 
OF  MILK  AND  DAIRY  PRODUCTS 

114.  Food  and  Milk  Secretion.  —  There  is  a  close 
relationship  between  milk  secretion  and  the  food 
supply.  It  was  formerly  believed  that  the  percent- 
age amounts  of  the  milk  solids  could  be  materially 
influenced  by  the  character  of  the  food  consumed. 
In  the  numerous  experiments  that  have  been  made, 
a  few  cases  showed  the  composition  of  the  milk  to  have 
been  influenced,  but  it  was  not  possible  in  most  cases 
to  materially  increase  or  decrease  the  percentage  of  fat 
or  other  constituents  of  the  milk.  The  total  amount 
of  all  of  the  compounds  present,  however,  can  be  ma- 
terially increased  by  judicious  feeding,  and  thus, 
while  it  is  not  possible  for  the  farmer  by  liberal  feed- 
ing to  increase  the  per  cent  of  fat  in  his  milk,  he 
practically  accomplishes  the  same  result  by  increas- 
ing the  amount  of  milk. 

It  was  formerly  believed  that  the  fat  in  the  food 
was  the  main  source  of  the  fat  in  the  milk.  A  good 
cow,  however,  will  produce  during  a  year  a  much 
larger  amount  of  fat  in  the  milk  than  she  consumes 
in  the  food,  showing  that  the  fats  are  in  part  pro- 
duced from  other  nutrients. 
126 


126  DAIRY  CHEMISTRY 

115.  Feeding  Fat.  —  The  investigations  that  have 
been  made  show  that  it  is  not  possible  to  increase 
either  the  percentage  or  the  total  amount  of  fat  in 
the  milk  for  any  appreciable  time  by  the  feeding  of 
fats  or  oils.     In  experiments  at  Cornell  University, 
the  Iowa  Experiment  Station,  and  other  institutions 
where  fats  have  been  fed  to  cows  even  at  the  rate  of 
two  pounds  or  more  per  day  of  tallow,  cotton-seed  oil, 
corn  oil,  or  other  fats,  the  fat  content  of  the  milk  was 
not  permanently  increased .     The  quality  of  the  milk 
fat  and  of  all  the  dairy  products  is,  however,  appre- 
ciably affected  by  the  foods  consumed;  and  while  the 
fats  and  other  compounds  do  not  pass  directly  from 
the  food   into   the   milk   unchanged,    the   character 
of  the  fats  and  other  nutrients  materially  influences 
the    quality    of    the    fat    globules   and   the   dairy 
products. 

116.  Production  of  Hard  Butters.  —  When  cotton- 
seed meal  is  fed  in  liberal  amounts  and  is  not  combined 
with  other  grains,  it  produces  a  hard  and  tallow- 
like   butter   having  a  melting  point  of  10°  higher 
than  average  butter.     Chemical  analysis  shows  that 
there  is  a  larger  percentage  of  stearin  and  palmitin 
in  such  butter.     When  cotton-seed  meal  is  combined 
with  other  food  stuffs  and  is  fed  in  small  amounts, 
it  exerts  but  little  influence  on  the  butter  product. 
Cotton-seed   meal   is   a    valuable    nitrogenous    food 
when  properly  combined  and  fed  with  other  food 
materials. 

Corn,  also,  if  fed  alone  and  in  large  amounts,  will 


FOOD  AND   QUALITY  OF  MILK  127 

produce  an  abnormally  hard  butter,  particularly  if  com- 
bined with  overripe,  coarse  dry  fodders.  This  tend- 
ency of  some  food  stuffs  to  produce  an  abnormal  butter 
is  eliminated  when  foods  are  properly  combined. 

117.  Production  of  Soft  Butters.  —  While  cotton- 
seed meal  produces  a  hard  butter,  linseed  meal,  the 
product  obtained  after  removing  the  oil  from  flax- 
seed,  produces  a  soft  butter  when  fed  alone  and  in 
large  amounts.     Cotton-seed  meal  and  linseed  meal 
have  somewhat  the  same  general  composition  ;  both 
are  rich  in  protein  and  fat,  but  when  fed  they  have 
directly  opposite  effects   upon  the  character  of  the 
butter. 

118.  Effects  of  Individual   Foods.  —  There   are    a 
number  of  individual  food  stuffs  that  have  a  notice- 
able effect  upon  the  quality  of  the  milk  and  butter. 
Gluten  meal,  a  product  obtained  in  the  manufacture 
of   cornstarch,   produces   a   softer  butter  than  corn 
meal  ;  oats,  when  fed  alone   and  in  large  amounts, 
produce  a  mediumly  firm  but  rather  crumbly  butter; 
when  oats  and  corn  are  fed  together,  the  quality  of 
the  butter  is  much  improved.     Wheat  by-products, 
as  shorts  and  bran,  produce  a  mediumly  firm  butter 
of  good  quality;  wheat  and  barley  coarsely  ground 
also  produce  normal  butter. 

There  is  but  little  difference  in  the  milk-producing 
power  of  the  different  farm  grains  when  fed  in  mixed 
rations.  Of  the  coarse  fodders,  clover  hay,  corn 
silage,  and  well-cured  corn  fodder  produce  the  largest 
flow  and  also  milk  of  the  best  quality  for  butter  and 


128  DAIRY  CHEMISTRY 

cheese  making  purposes.  These  coarse  fodders,  when 
prepared  under  the  most  favorable  conditions,  pro- 
duce mediumly  firm  butter  in  contrast  to  the  hard 
and  tallow-like  butter  produced  from  overripe  hay 
containing  a  large  amount  of  fiber  and  but  little  pro- 
tein. Silage  has  been  found  to  be  of  much  value  in 
a  ration,  as  it  produces  a  better  quality  of  butter 
than  average  coarse  fodders.  It  has  been  objected 
to  by  some  because  of  the  silage  odor  of  the  milk.  It 
has  been  found  that  this  is  due  largely  to  lack  of 
proper  ventilation  in  the  stable,  as  the  silage  odor 
gains  access  mainly  at  the  time  of  milking  rather  than 
being  transmitted  through  the  milk.  When  animals 
are  kept  under  the  most  sanitary  conditions  and 
silage  forms  only  a  part  of  the  ration,  there  is  no 
perceptible  odor  to  the  milk  and  it  is  of  good 
quality.  As  previously  stated  (section  75),  some 
food  stuffs,  as  turnips,  rape,  and  onions,  affect  the 
flavor  of  the  milk.  This  is  due  to  the  volatile  and 
essential  oils  passing  directly  from  the  food  into  the 
milk.  There  are  weeds  that  are  also  responsible  for 
bad-tasting  milk,  as  the  wild  garlic,  which  produces  a 
foul  tas,te. 

119.  Desirable  Flavors  in  Milk  Products.  —  The 
desirable  flavors  in  butter,  cheese,  and  other  dairy 
products  are  due  to  the  small  amount  of  chemical 
compounds  formed  by  the  workings  of  the  bacterial 
ferments  and  the  enzymes.  As  a  result  of  fermen- 
tation action,  definite  chemical  compounds,  some  of 
which  have  pleasant  and  desirable  properties  and 


FOOD  AND   QUALITY  OF  MILK  129 

others  undesirable  ones,  are  produced.  Butyric  acid 
fermentation  is  an  example  of  the  undesirable  kind 
and  results  in  the  production  of  butyric  acid,  which 
gives  stale  butter  its  characteristic  odor.  By  con- 
trolling the  processes  of  fermentation  during  the 
manufacture  of  dairy  products,  the  undesirable  fer- 
ments are  prevented  from  gaining  access  to  the  milk, 
and  the  desirable  ferments  are  added  and  given  every 
opportunity  to  carry  on  the  normal  processes  of  fer- 
mentation. Fresh,  normal  milk  should  have  a  pleas- 
ant taste,  and  when  obtained  and  handled  in  a  cleanly 
way,  it  will  contain  but  few  bacterial  bodies. 

120.  Influence  of  Balanced  Rations.  —  When  the 
animal  body  is  supplied  with  the  necessary  nutrients 
for  the  various  functional  purposes,  the  largest 
amount  and  the  best  quality  of  milk  is  secured.  It 
is  only  when  unusual  food  stuffs  and  those  deficient 
in  the  requisite  nutritive  materials  are  fed  that  milk 
of  abnormal  character  is  produced.  One  of  the 
objects  of  combining  several  grains  and  coarse  fod- 
ders to  form  a  balanced  ration  is  to  furnish  the 
nutrients  to  produce  the  largest  amount  and  best 
quality  of  milk.  Much  experimental  work  has  been 
done  to  ascertain  the  relationship  between  the  vari- 
ous food  stuffs  and  milk  secretion.  It  was  believed 
at  one  time  that  certain  foods  contained  special  com- 
pounds which  stimulated  milk  secretion.  It  has 
been  found,  however,  that  there  are  no  special  foods 
which  exert  an  influence  on  milk  secretion  not  shared 
alike  by  the  common  farm  grains  and  well-prepared 


130  DAIRY   CHEMISTRY 

fodders.  There  are  no  stock  foods  that  possess  prop- 
erties for  increasing  the  secretion  or  flow  of  milk. 
The  best  results  are  secured  by  supplying  a  variety 
of  food  stuffs  containing  a  liberal  amount  of  nutri- 
tive materials.  Milk  produced  under  the  best  sani- 
tary conditions  from  healthy  and  well-fed  animals 
has  an  individuality,  and  such  milk  is  specially  valu- 
able for  food  and  for  the  manufacture  of  butter 
and  cheese. 

121.  Milk  Secretion.  —  The  materials  of  which  milk 
is  composed  are  abstracted  from  the  blood,  and  in 
order  to  keep  up  a  good  flow  of  milk  suitable  food 
should  be  supplied,  which  may  be  later  elaborated 
into  milk.  Some  animals  are  so  constituted  that  the 
food  supply  is  used  for  the  production  of  fat  and 
increase  in  weight  rather  than  for  milk  production. 
Such  animals  are  not  profitable  for  dairy  purposes. 

There  are  a  number  of  factors  that  influence  milk 
secretion,  as  regularity  of  milking  and  feeding, 
manipulation  of  the  udder,  exhaustive  milking,  pro- 
tection of  the  animals  from  sudden  changes  in  tem- 
perature and  adverse  climatic  conditions,  and  good 
sanitary  surroundings.  These  factors  all  influence 
the  secretion  of  milk,  because  the  process  is  largely 
the  result  of  the  working  of  individual  cells  which 
compose  the  ultimate  follicles,  and  in  case  the  cells 
are  injured  or  are  not  given  the  best  conditions  for 
doing  their  work,  milk  secretion  is  decreased  and  the 
quality  of  the  product  lowered. 


CHAPTER  XIV 

THE  RATIONAL  FEEDING  OF  DAIRY  STOCK 

122.  Uses  of  Food.  —  Food  is  used  by  the  animal 
body   for   three   purposes  :    (1)    for   production    of 
heat  and  energy  ;     (2)  for  growth  and  to  furnish 
materials  to  renew  the  worn-out  tissues  of  the  body ; 
and  (3)  for  the  production  of  animal  products,  as 
milk,  meat,  and  wool.     When  the  animal  body  has 
been  supplied  with  food  for  heat,  energy,  and  growth, 
the  excess  is  then  available  for  the  production  of 
meat   and   milk.     The  different   nutrients   or  com- 
pounds of  which  foods  are  composed  serve  different 
functions  in  the  body,  and  in  the  rational  feeding  of 
farm  animals  it  is  the  object  to  combine  various  food 
stuffs  so  that  the  nutrients  will  be  present  in  the 
right  amounts  and  proportions  for  the  various  func- 
tions of  the  body. 

123.  Nutrients  and   their   Functions.  —  The   com- 
pounds  of   which  foods   are    composed  are  divided 
into   two   main  classes,  the  nitrogen-containing  or 
nitrogenous   compounds,    and    those    containing   no 
nitrogen  or  the  non-nitrogenous  compounds.      The 
nitrogenous  compounds  are  spoken  of  collectively  as 
the  crude  protein  of  food  stuffs  ;    the  non-nitroge- 
nous compounds  are  mainly  starch,  sugar,  fat,  and 

131 


132  DAIRY  CHEMISTRY 

cellulose.  The  two  classes  of  compounds,  nitroge- 
nous and  non-nitrogenous,  serve  different  functional 
purposes  in  the  body.  The  nitrogenous  compounds, 
or  proteids,  are  the  more  expensive  and  are  present 
in  much  smaller  amounts  than  the  non-nitrogenous 
compounds.  Starch,  sugar,  fiber  or  cellulose,  and 
allied  bodies,  are  spoken  of  collectively  as  the  car- 
bohydrates, and  in  connection  with  feeding  stuffs 
only,  the  three  general  terms,  "  crude  protein,"  "  car- 
bohydrates," and  "  crude  fat "  or  "  ether  extract,"  are 
employed.  Food  stuffs  are  composed  of  a  great  many 
other  compounds  besides  these  general  classes. 

124.  Dry  Matter.  —  When  a  substance  is  dried  at 
a  temperature  of  212°  F.,  all  of  the  water  is  removed, 
and  what  is  left  is  called  dry  matter.    All  food  stuffs 
contain  some  water.     Grains  and  mill  products  con- 
tain from  10  to  15  per  cent  of  water,  dry  hay  from  12 
to  18  per  cent,  and  roots  and  tubers  from  75  to  90 
per  cent.     Some  green  crops  and  vegetables  contain 
as  high  as  95  per  cent  of  water.     The  dry  matter  of 
a  food  is  simply  a  mechanical  mixture  of  the  differ- 
ent compounds  of  which  the  material  is  composed, 
as  ash  or  mineral  matter,   crude  protein,   and  non- 
nitrogenous  compounds,  including  carbohydrates  and 
crude  fats. 

125.  Ash.  —  When   the  dry   matter  of  a  food   is 
burned   at   the    lowest    temperature    necessary    for 
complete  combustion,  the  ash  or  mineral  matter  is 
obtained.     In  most  agricultural  plants  the  ash  is  less 
than  10  per  cent  of  the  dry  matter,  and  in  the  grain 


THE  RATIONAL  FEEDING   OF  DAIRY  STOCK     133 

crops  it  ranges  from  2  to  4  per  cent.  The  ash  is 
composed  of  lime,  potash,  phosphates,  and  other 
mineral  substances.  All  of  the  coarse  fodders,  grains, 
and  mill  products  contain  a  sufficient  amount  of 
mineral  matter  for  purposes  of  nutrition,  including 
phosphates  for  bone  formation  and  for  the  production 
of  milk. 

126.  The   Organic   Matter.  —  That  portion  of  the 
dry  matter  which  is  burned  and  converted  into  vola- 
tile  products   is   called   the  organic   matter.     It  is 
obtained  by  subtracting  the  per  cent  of  ash   from 
100,    which    represents    the    total   amount   of    dry 
substance. 

127.  Proteids.  —  These  compounds,  which  are  found 
in  variable  amounts  in  all  food  stuffs,  are  similar  in 
general  composition  to  the  milk  proteids  described 
in  section  82.     The  proteids  as  a  class  are  character- 
ized by  containing  the  element  nitrogen  in  addition 
to  carbon,  hydrogen,  and  oxygen,  which  are  present 
in  all  the  other  nutrients  of  food  stuffs.     It  is  the 
proteids  which  serve  the  special  purpose  of  supplying 
the  materials  for  repairing  the  body  waste.     Proteids 
are  the  principal  materials  out  of  which  the  muscles 
are   formed,   and   they  also   enter  largely   into   the 
composition  of  all  the  tissues  of  the  body.     All  the 
vital  fluids  of  the  body,  as  the  blood,  contain  large 
amounts  of  this  class  of  compounds.     The  proteids 
of  the  body  can  be  formed  only  from  the  proteids  of 
the   food ;    hence   the  importance   of   the   requisite 
supply  of  this  nutrient  in  the  food.     An  excessive 


134  DAIRY  CHEMISTRY 

amount,  however,  in  a  ration  is  unnecessary.  After 
the  functions  of  the  body  are  served,  the  surplus 
protein  is  used  for  producing  heat  and  energy,  and 
it  quite  frequently  happens  that  a  ration  is  unneces- 
sarily expensive  because  of  containing  an  excess  of 
protein,  which  is  used  for  the  production  of  heat 
where  cheaper  nutrients,  as  the  carbohydrates,  would 
serve  the  same  purpose.  Neither  is  a  ration  that 
contains  too  scant  an  amount  economical,  as  a  full 
milk  flow  cannot  be  maintained  on  a  scant  supply  of 
protein.  The  rational  feeding  of  animals  is  largely 
a  regulation  of  the  supply  in  the  food  of  proteids  and 
carbohydrates  for  milk  production  and  other  pur- 
poses. There  are  a  great  many  different  kinds  of 
proteids  in  food  stuffs.  Casein  and  albumin  in  milk 
are  proteids ;  egg  albumin  is  also  a  proteid.  The 
glutens  of  wheat  and  other  grains  are  among  the 
most  common  proteids  found  in  food  stuffs. 

128.  Carbohydrates.  —  With  the  exception  of  fat, 
all  the  non-nitrogenous  compounds,  as  sugar,  starch, 
and  cellulose,  taken  collectively,  are  called  carbo- 
hydrates. By  far  the  largest  part  of  the  nutrients 
in  food  stuffs  are  carbohydrates.  Those  carbo- 
hydrates which  ane  easily  rendered  soluble,  as  sugar 
and  starch,  are  called  the  nitrogen-free-extract  com- 
pounds. Carbohydrates  are  a  complex  group  of 
substances  composed  of  three  elements,  —  carbon, 
hydrogen,  and  oxygen.  The  chief  function  of  the 
carbohydrates  is  to  produce  heat  and  energy,  and, 
when  properly  combined  with  the  proteids,  they  may 


THE  RATIONAL  FEEDING  OF  DAIRY  STOCK     135 

serve  for  the  production  of  fat  in  the  body.  The 
carbohydrates  from  different  food  stuffs  vary  widely 
in  character.  In  the  potato,  starch  is  the  main  carbo- 
hydrate ;  in  beets,  it  is  sugar ;  in  apples,  pectose  or 
jellylike  substances;  and  in  hay  and  coarse  fodders, 
pentosans  predominate,  or  bodies  that  can  be  con- 
verted into  sugarlike  substances  containing  five 
atoms  of  carbon  in  the  molecule. 

129 .  Crude  Fiber. — The  term  "  crude  fiber  "  is  applied 
to  the  cellular  tissues  of  which  the  framework  of 
plants  is  composed.     A  portion  of  the  fiber  is  digest- 
ible and  capable  of  serving  the  same  functions  as  the 
soluble  carbohydrates.     Foods  with  excessive  amounts 
of  fiber  are  objectionable,  but  on  the  other  hand  some 
fiber  is  desirable  in  order  to  give  the  necessary  bulk 
to  a  ration. 

130.  Crude   Fat.  —  All   food   stuffs   contain  some 
fatty  compounds.     In  farm  grains  from  2  to  5  per 
cent  of  ether  extract  or  crude  fat  is  present ;  in  coarse 
fodders  from  1|  to  2.25  per  cent;  while  in  some  of 
the  specially  prepared  mill  products,  as  oil  meal,  10 
per  cent   or  more  of  fat  may  be  present.     The  fat 
in  food  stuffs  is  extracted  with  ether,  and  hence  the 
term  "ether  extract "  is  used.     In  addition  to  the  fats, 
ether  extract   contains  small  amounts  of  other  sub- 
stances, as  chlorophyll  and  resin.     Hence  the  ether 
extract  is  not  pure  fat.     From  grains  and  mill  prod- 
ucts, however,  the  ether  extract  is  nearly  pure  fat, 
while  in  that  from  coarse  fodders  there  is  only  from 
50  to  75  per  cent  of  pure  fat.     Fats  are  character- 


136  DAIRY  CHEMISTRY 

ized  by  containing  a  larger  amount  of  carbon  than 
either  starch  or  sugar,  and  hence,  when  burned  or 
digested  in  the  body,  they  produce  a  larger  amount 
of  heat  and  energy.  A  pound  of  fat  will  produce 
2.25  times  as  much  heat  as  a  pound  of  starch. 

131.  Digestible  Nutrients.  —  Only  a  portion  of  the 
compounds  of  which  foods  are  composed  is  digested, 
absorbed  by  the  body,  and  used  for  some  functional 
purpose.       In  average  food  stuffs  from  15  to  45  per 
cent  of  the  nutrients  are  indigestible  and  unavailable 
to  the  body.      That  portion  of  a  compound  which 
is     digested    and    utilized    is    called    a    digestible 
nutrient.     Foods  contain  digestible  protein,  digest- 
ible fats,  and  digestible   carbohydrates.     The  total 
nutrients  are  only  in  part  digestible.     The  digestible 
nutrients  of  a  food  stuff  are  determined  by  means  of 
digestion  experiments,  in  which  the  income  and  outgo 
of  the  nutrients  of  the  food,  including  the  amount 
which  fails  to  digest,  are  accurately  determined.     As 
a   result   of    numerous    digestion    experiments,    the 
digestion   coefficients  or  the  percentage  of  the  nu- 
trients that  are  digested  are  determined.    The  diges- 
tion  coefficients   are   used   for   the   construction  of 
tables   of   digestible   nutrients  in   foods.     In    using 
these  tables  in  rational  feeding,  it  is  only  the  digest- 
ible nutrients  that  are  to  be  considered,  as  the   in- 
digestible portion  of  the  food  furnishes  no  material 
for  functional  purposes. 

132.  Caloric  Value  or   Heat  Units  of  a  Ration.— 
When    food    is  digested,  heat  is  produced  and    the 


THE  RATIONAL  FEEDING   OF  DAIRY  STOCK      137 

amount  of  heat  is  directly  proportional  to  the  per- 
centage of  fat,  carbohydrates,  and  proteids  present. 
A  balanced  ration  produces  about  32,000  calories,  or 
heat  units.  A  calory  is  the  unit  of  heat,  or  the 
amount  of  heat  required  to  raise  1  kg.  of  water  1° 
on  the  centigrade  scale,  or  one  pound  of  water  about 
4°  on  the  Fahrenheit  scale.  A  pound  of  digestible 
fat  produces  4225  calories,  and  a  pound  of  digest- 
ible carbohydrates  or  protein  produces  1860  calories. 

133.  Nutritive  Ratio.  — The  term  "nutritive  ratio " 
is  used  to  express  the  ratio  which  exists  between  the 
digestible  protein  and  the  digestible  carbohydrates. 
A  nutritive  ratio  of  1  to  6.5  means  that  there  is  one 
part  of  digestible  protein  to  6.5  parts  of  digestible, 
non-nitrogenous  compounds.     A  wide  ration  means 
a   large   proportional   amount   of    carbohydrates   to 
protein,   while  a  narrow   ration  means   a  compara- 
tively small  amount  of  digestible  carbohydrates  to 
protein.     In  calculating  the  nutritive  ratio,  the  crude 
fat  or  ether  extract  is  multiplied  by  2.25,  because 
the  fats  are  2.25  times  more  concentrated  than  the 
carbohydrates. 

134.  Selection  of  Foods  for  Rations.  —  In  the  feed- 
ing of  dairy  animals  the  selection  of  the  food  mate- 
rials  is   of   equal   importance  with   the  amount   of 
nutrients  they  contain,  because,  as  stated  in  a  pre- 
ceding chapter,  the  amount  and  quality  of  the  milk 
and  products  are  dependent  largely  upon  the  charac- 
ter of  the  foods  consumed.     To  give  the  best  results, 
a  ration  should  contain  grains,  mill  products,  coarse 


138  DAIRY  CHEMISTRY 

fodders,  and  roots  blended  in  such  a  way  as  to  meet 
all  the  requirements  of  the  body.  A  ration  should 
have  the  requisite  bulk,  be  palatable,  and  contain  a  va- 
riety of  food  materials  with  sufficient  digestible  nutri- 
ents. The  coarse  fodders  most  satisfactory  for  dairy 
feeding  are  clover  hay,  alfalfa,  corn  fodder,  corn  si- 
lage, oat  hay,  and  the  best  grades  of  timothy,  upland, 
and  prairie  hay.  Common  farm  grains,  as  barley, 
oats,  and  corn  are  equally  as  valuable  for  milk  pro- 
duction as  the  common  mill  products,  —  bran  and 
shorts.  Farm  grains,  however,  are  not  quite  as  valu- 
able pound  for  pound  as  the  more  concentrated  mill 
products,  such  as  oil  meal  and  cotton-seed  meal. 
The  quantity  of  food  an  animal  receives  should 
vary  with  the  amount  of  milk  produced.  When  an 
animal  is  giving  a  full  flow  of  milk,  the  maximum 
amount  of  food  should  be  supplied.  A  standard 
ration  or  one  for  a  cow  giving  25  to  30  pounds  of 
milk  should  contain  from  1.7  to  2  pounds  of  digest- 
ible protein  and  about  14  pounds  of  digestible  carbo- 
hydrates per  day.  Such  a  ration  will  produce  about 
32,000  calories  or  heat  units.  A  ration  that  is  well 
suited  for  dairy  purposes  will  return  from  10  to  12 
per  cent  of  the  dry  matter  of  the  food  in  the  milk. 
About  one  quarter  of  the  protein  in  the  food  of  a 
milk  cow  is  used  for  maintenance  purposes,  about 
one  half  for  the  production  of  the  milk,  and  about 
one  quarter  is  voided  as  indigestible.  It  is  not  pos- 
sible to  formulate  definite  standards  in  the  feeding 
of  dairy  stock  that  are  alike  applicable  to  all  animals 


THE  RATIONAL  FEEDING   OF  DAIRY  STOCK     139 

and  all  conditions.  The  quantity  of  food  that  can 
be  consumed  to  the  best  advantage  must  be  deter- 
mined experimentally  by  the  feeder  and  should  be 
varied  as  occasion  demands  in  order  to  give  the  best 
results.  Ordinarily  a  ration  of  from  7  to  10  pounds 
of  farm  grains  and  mill  feeds,  with  18  to  25  pounds 
of  mixed  coarse  fodders,  will  supply  approximately 
the  requisite  amount  of  nutrients  for  the  production 
of  milk.  There  is  but  little  difference  in  the  milk- 
producing  value  of  the  different  farm  grains  when 
fed  in  mixed  rations.  For  economical  production, 
as  much  of  the  digestible  protein  as  possible  should 
be  supplied  in  the  coarse  fodders,  so  as  to  reduce  the 
quantity  of  grains  that  are  required  for  feeding 
purposes. 

135.  How  to  calculate  a  Ration.  —  The  foods  that 
are  to  be  combined  to  form  the  ration  should  be 
selected  on  the  basis  of  cost  and  composition.  In 
case  corn  fodder,  clover  hay,  oats,  corn,  and  mangels 
are  raised  on  the  farm,  these  foods  can  be  combined 
to  form  a  balanced  ration  either  with  or  without  any 
commercial  foods.  In  case  it  is  desired  to  make  a 
ration  of  these  foods  with  bran,  the  general  state- 
ments given  in  paragraph  134  as  to  quantities  of 
food  should  be  noted.  About  20  pounds  of  coarse 
fodder,  10  to  12  pounds  of  grains,  and  10  pounds  of 
mangels  will  form  the  roughage  of  a  reasonably  well- 
balanced  ration  for  a  cow  giving  from  25  to  30 
pounds  of  milk  per  day.  The  digestible  nutrients 
in  100  pounds  of  the  foods  combined  are  first  noted. 


140 


DAIRY  CHEMISTRY 


As  given  in  the  table  in  the  Appendix,  they  contain 
the  following  amounts  of  digestible  nutrients  :  — 


DIGESTIBLE  NUTRIENTS  IN  100  LB.  or 
FOOD  MATERIALS 

Protein 

Carbohydrates 

Fats 

2.5 
6.8 
9.2 
7.9 
12.9 
1.1 

34.6 
35.8 
47.3 
66.7 
40.1 
5.4 

1.2 
1.7 
4.2 
4.3 
3.4 
0.1 

Clover  hay  

Oats    

Bran   

Since  the  figures  represent  the  amounts  of  digestible 
protein,  carbohydrates,  and  fats  in  100  pounds  of  the 
foods,  the  amount  of  digestible  nutrients  in  1  pound 
is  obtained  by  moving  the  decimal  point  two  places 
to  the  left.  A  trial  ration  is  first  made  with  10 
pounds  each  of  corn  fodder,  clover  hay,  and  mangels, 
and  7  pounds  of  oats,  3  of  corn,  and  2  of  bran.  The 
pounds  of  digestible  protein,  carbohydrates,  and  fats 
in  10  pounds  of  the  corn  fodder,  clover  hay,  and  man- 
gels are  obtained  by  moving  the  decimal  point  one 
place  to  the  left.  The  pounds  of  digestible  protein 
in  the  7  pounds  of  oats  are  obtained  by  multiply- 
ing .092  by  7,  and  the  pounds  of  digestible  carbo- 
hydrates by  multiplying  .473  by  7,  and  the  fat  by 
multiplying  .042  by  7.  In  like  manner,  the  digest- 
ible nutrients  in  the  3  pounds  of  corn  and  the 


THE  RATIONAL  FEEDING   OF  DAIRY  STOCK     141 


2  pounds  of  bran  are  obtained  by  multiplying  the  per 
cent  of  each  digestible  nutrient  by  the  weight  of  the 
material  used.  The  pounds  of  digestible  protein,  car- 
bohydrates, and  fat  in  the  several  foods  are  as  follows: 


TOTAL  DIGESTIBLE  NUTRIENTS 

Protein 

Carbohydrates 

Crude  Fats 

Corn  fodder, 

10  Ib.  .     .     . 

0.25 

3.50 

0.12 

Clover  hay, 

10  Ib.  .     .     . 

0.68 

3.58 

0.17 

Mangels, 

10  Ib.  .     .    . 

0.01 

0.05 

— 

Oats, 

7  Ib.  .     .     . 

0.65 

3.31 

0.29 

Corn, 

3  Ib.  .     .    . 

0.24 

1.99 

0.12 

Bran, 

2  Ib.  .     .     . 

0.25 

0.80 

0.06 

Total      . 

2.08 

13.23 

0.76 

.76  x  2.25  =  1.71 ;   13-2?  +  !-71  =  7  nutritive  ratio. 

Heat  units:  (13.23  +  2.08)  x  1860  =  28,476.6 

.76  x  4225  =    3,211.0 

Total  31,687.6 

This  ration  contains  2.08  pounds  of  digestible  pro- 
tein, 13.23  pounds  of  digestible  carbohydrates,  and 
.76  pound  of  digestible  fats.  The  nutritive  ratio 
is  1  to  7,  and  the  ration  yields  a  total  of  31,687.6 
calories.  Compared  with  the  requirements  of  a 
standard  ration  for  a  cow  giving  25  to  30  pounds 
of  milk,  it  will  be  found  that  these  amounts  con- 
form sufficiently  to  the  standard  to  warrant  this 
ration  being  used.  It  is  to  be  noted  that  the  pro- 


142  DAIRY  CHEMISTRY 

tein  is  largely  supplied  by  the  clover  hay  and  oats, 
and  the  carbohydrates  in  nearly  equal  amounts  by 
the  corn  fodder,  clover  hay,  and  oats.  Corn  and 
bran  are  used  in  smaller  quantities,  but  add  appre- 
ciable amounts  of  digestible  nutrients  to  the  ration. 
While  the  mangels  do  not  supply  a  large  amount  of 
nutrients,  they  are  very  valuable  in  the  ration  in 
other  ways.  They  impart  palatability  and  promote 
secretion  of  the  gastric  and  digestive  fluids.  In 
case  a  smaller  amount  of  milk  is  produced,  the  quan- 
tity of  grain  should  be  reduced.  If  more  than  30 
pounds  of  milk  are  given,  the  grain  part  of  the  ration 
should  be  proportionally  increased.  The  ration  con- 
tains a  sufficient  variety  of  food  materials,  and  the 
foods  are  combined  in  such  a  way  as  to  produce  a 
good  quality  of  milk.  It  is  not  necessary  that  a 
ration  should  conform  absolutely  with  the  tables. 
A  variation  of  .1  to  .2  of  a  pound  of  protein  in  a 
ration,  provided  there  is  a  corresponding  increase 
in  the  other  nutrients,  will  not  seriously  affect  the 
milk-producing  power  of  the  ration. 

The  figures  given  in  the  Appendix  represent  the 
average  composition  of  feeding  stuffs,  as  found  by 
a  number  of  experiment  stations.  Individual  sam- 
ples of  coarse  fodders  may  vary  appreciably  from  the 
average  that  is  given.  For  example,  it  is  possible  for 
corn  fodder  to  contain  as  low  as  1-5  pounds  of  digest- 
ible protein  per  100,  or  as  high  as  3.5  pounds.  When 
the  coarse  fodders  are  raised  on  rich  soil  and  prepared 
under  the  best  conditions  and  cut  when  not  overripe. 


THE  RATIONAL  FEEDING   OF  DAIRY  STOCK     143 

they  will  contain  the  maximum  amount  of  nutritive 
materials,  and  such  fodders  can  be  used  in  appreci- 
ably less  amounts  than  fodders  grown  under  less 
favorable  conditions  and  which  contain  more  fiber 
and  less  digestible  protein  and  carbohydrates.  Be- 
cause of  differences  in  the  quality  of  the  same  class 
of  fodders,  it  is  possible  for  two  farmers  to  feed  the 
same  kinds  of  feeding  stuffs  and  grains  and  yet 
secure  widely  different  return  in  milk  yields. 

While  it  is  not  necessary  to  conform  too  closely  to 
the  standards  in  the  feeding  of  dairy  stock,  a  wide 
variation  is  not  desirable,  as  milk  cannot  be  produced 
economically  when  the  stock  is  not  fed  on  reasonably 
well-balanced  rations,  and  the  quality  of  the  product 
is  often  abnormal.  Numerous  experiments  have  been 
made  to  determine  the  rations  that  are  most  suitable 
for  milk  production.  It  has  been  found  that  a  com- 
paratively narrow  ration  of  1  to  5.5  will  produce  a 
larger  flow  of  milk  than  a  wider  ration  of  1  to  8. 
But  if  the  narrow  ration  is  fed  in  large  amounts,  the 
milk  is  not  produced  as  economically  as  when  the 
wider  ration  is  fed.  Maximum  returns  are  secured 
when  a  ration  is  fed  which  has  a  nutritive  ratio  of 
from  1  to  6.5  or  7.5.  It  frequently  happens  in  the 
feeding  of  dairy  stock  that  heavy  grain  rations  are 
not  economical  because  the  excess  of  protein  is  not 
used  for  vital  purposes,  but  serves  a  purpose  which 
would  be  as  well  served  by  the  use  of  the  cheaper 
carbohydrates.  In  the  case  of  young  stock  it  is  ad- 
vantageous to  feed  a  liberal  ration,  as  this  will  have 


144  DAIRY  CHEMISTRY 

a  tendency  to  encourage  a  larger  flow  of  milk  dur- 
ing later  periods  of  lactation. 

In  the  feeding  of  dairy  stock,  sudden  changes  in 
the  ration  should  be  avoided.  In  case  it  is  necessary 
to  make  a  change  in  the  coarse  fodder  or  grains,  it 
should  be  done  gradually.  A  good  feeder  can  tell 
from  the  appearance  of  the  stock  and  the  avidity 
with  which  the  ration  is  consumed  whether  the 
grains  and  coarse  fodders  are  being  fed  to  advan- 
tage. In  many  of  the  feeding  trials  that  have  been 
made,  the  experimental  periods  have  been  too  short 
to  give  reliable  results. 

136.  Comparative  Cost  and  Value  of  Grains.  —  The 
market  and  feeding  value  of  grains  often  vary  between 
wide  extremes,  and  it  is  frequently  found  that  a  given 
sum  of  money,  if  invested  in  one  food,  will  procure  a 
larger  amount  of  digestible  nutrients  than  if  invested 
in  other  foods.  In  general,  it  can  be  said  that  there 
is  but  little  difference  in  the  milk-producing  value 
of  grains  when  fed  in  a  mixed  ration,  and  hence  the 
price  per  pound  can  be  taken  as  the  deciding  factor 
as  to  what  shall  constitute  the  main  part  of  the  ration. 
In  case  it  is  desired  to  compare  the  amount  of  nutri- 
ents that  can  be  procured  for  a  given  sum  of  money, 
it  can  be  done  in  the  following  way :  Determine  the 
number  of  pounds  of  food  material  that  can  be  pur- 
chased for  $1.00,  and  then  calculate  the  number  of 
pounds  of  digestible  nutrients  in  this  quantity  of  food. 
For  example,  if  oats  are  30  cents  per  bushel,  a  dollar 
will  purchase  107  pounds.  Since  100  pounds  of 


THE  RATIONAL   FEEDING   OF  DAIRY  STOCK     145 

oats  contain  9.2  pounds  of  digestible  protein,  4.2 
pounds  of  fat  and  47.3  pounds  of  digestible  carbo- 
hydrates, 107  pounds  will  be  found  to  contain  9.84 
pounds  of  protein,  4.5  pounds  of  fat,  and  50.6  pounds 
of  carbohydrates.  In  case  it  is  desired  to  compare  the 
nutrients  in  oats  at  30  cents  per  bushel  with  the  nu- 
trients in  corn  at  50  cents  per  bushel,  the  same  pro- 
cess of  calculation  is  carried  on.  One  dollar  will 
purchase  112  pounds  of  corn,  and  since  100  pounds 
contain  protein,  fat,  and  carbohydrates  in  the  pro- 
portion given  in  section  135,  112  pounds  will  con- 
tain 8.85  pounds  of  protein,  4.83  pounds  of  fat,  and 
74.7  pounds  of  carbohydrates.  The  107  pounds  of 
oats  contain  about  a  pound  more  digestible  protein 
than  the  112  pounds  of  corn,  but  on  the  other  hand 
the  corn  contains  about  24  pounds  more  digestible 
carbohydrates.  For  ordinary  purposes  of  feeding,  a 
larger  return  will  be  secured  from  24  pounds  of  car- 
bohydrates than  from  1  pound  of  protein.  If,  how- 
ever, the  ration  contains  a  scant  amount  of  protein, 
then  preference  should  be  given  to  the  protein.  But 
at  the  price  stated,  corn  could  be  used  more  econom- 
ically than  the  oats.  In  determining  the  compara- 
tive value  of  two  grains,  preference  should  always  be 
given  to  the  protein  ;  but  in  case  the  difference  in  the 
amount  of  digestible  protein  that  can  be  purchased 
for  $1.00  is  not  large,  while  the  difference  in  digest- 
ible carbohydrates  is  quite  large,  then  the  food  that 
contains  the  smaller  amount  of  protein,  but  larger 
amount  of  carbohydrates,  would  be  the  cheaper  food. 


146  DAIRY  CHEMISTRY 

In  the  combination  of  foods  to  form  balanced 
rations  there  are  a  number  of  factors  that  should 
receive  consideration.  The  foods  should  be  in  the 
best  mechanical  condition.  In  the  case  of  some 
grains,  coarse  grinding  should  be  practiced.  Seeds 
with  hard  seed  coats,  as  wheat  and  barley,  should 
be  coarsely  ground,  particularly  if  the  animals  are 
giving  large  amounts  of  milk.  If  the  animals  are 
giving  a  smaller  quantity  of  milk,  grinding  is  not 
so  necessary,  as  more  energy  can  then  be  profitably 
expended  in  the  mastication  of  the  food.  In  order 
to  meet  with  success  in  feeding,  practical  experience 
in  the  handling  of  stock  is  necessary.  Too  frequently 
the  foods  are  portioned  out  by  volume  rather  than  by 
weight,  and  the  feeder  has  but  little  knowledge  as  to 
the  weight  of  the  food  he  is  feeding.  Since  the  weight 
per  bushel  of  grains  varies  so  widely,  volume  or  meas- 
ure is  a  very  unsafe  basis  for  portioning  out  food. 
For  example,  a  quart  of  corn  will  weigh  much  more 
than  a  quart  of  oats,  although  a  pound  of  oats  will 
contain  more  digestible  protein  than  a  pound  of  corn. 
It  makes  a  great  difference  in  the  amount  of  digest- 
ible nutrients  which  the  animals  receive  when  the 
foods  are  portioned  out  by  volume  instead  of  by 
weight. 

In  the  feeding  of  dairy  stock,  the  sanitary  con- 
ditions discussed  in  Chapter  VIII  must  be  taken  into 
consideration,  because  the  best  returns  cannot  be  se- 
cured from  foods  when  the  animals  are  not  cared  for 
under  the  most  sanitary  conditions. 


APPENDIX 


DIGESTIBLE   NUTRIENTS   IN   FODDERS 


NAME  OF  FEED 

DRY 

MATTER 

IN 

100  LB. 

DIGESTIBLE  NUTRIENTS 
IN  100  LB. 

PROTEIN 

CARBOHY- 
DRATES 

ETHER 
EXTRACT 

Corn  (all  analyses)  .... 
Dent  corn  

89.1 
89.4 
88.7 
91.2 
89.3 
84.9 
90.9 
91.8 
89.6 
88.9 
89.5 
88.1 
88.5 
87.7 
88.2 
87.9 
88.4 
88.4 
88.4 
90.7 
89.1 
89.8 
24.3 
91.8 
89.0 
92.3 

7.9 
7.8 
8.0 
8.8 
0.4 
4.4 
7.4 
25.8 
9.0 
7.5 
10.2 
12.2 
12.9 
12.3 
12.2 
12.8 
9.8 
9.9 
11.5 
11.9 
8.7 
18.6 
3.9 
15.7 
9.2 
12.5 

66.7 
66.7 
62.2 
63.7 
52.5 
60.0 
59.8 
43.3 
61.2 
55.2 
69.2 
39.2 
40.1 
37.1 
50.0 
53.0 
51.0 
67.6 
50.3 
45.1 
65.6 
37.1 
9.3 
36.3 
47.3 
46.9 

4.3 

4.3 
4.3 
7.0 
0.3 
2.9 
4.6 
11.0 
6.2 
6.8 
1.7 
2.7 
3.4 
2.6 
3.8 
3.4 
2.2 
1.1 
2.0 
1.6 
1.6 
1.7 
1.4 
5.1 
4.2 
2.8 

Corn  and  cob  meal  .... 

Gluten  meal    

Wheat                  

Wheat  bran 

Wheat  bran  (spring  wheat) 
Wheat  bran  (winter  wheat) 
Wheat  shorts  

Wheat  middlings     .... 
Wheat  screenings    .... 
Rve 

Rye  bran    

Barley    

Brewer's  grains  (wet)  .     .    . 
Brewer's  grains  (dried)    .     „ 
Oats  

Oat  feed  or  shorts    .... 

147 


148 


DAIRY  CHEMISTRY 


DIGESTIBLE   NUTRIENTS   IN   FODDERS  —  Continued 


NAME  OF  FEED 

DRY 

MATTER 

IN 

100  LB. 

DIGESTIBLE  NI-TRIEXTS 
IN  100  LB. 

PROTEIN 

CARBOHY- 
DRATES 

ETHER 
EXTRACT 

Oat  hulls 

90.6 
87.4 
89.5 
90.8 
90.8 
89.9 
91.8 

20.7 
57.8 
59.5 

20.0 
34.9 
38.4 
37.8 
16.0 

86.8 
91.1 
78.8 
92.3 
87.1 
83.4 
91.1 

90.4 
90.8 

1.3 

7.7 
7.4 
20.6 
29.3 
28.2 
37.2 

1.0 
2.5 
1.7 

2.5 
3.0 
1.2 
2.6 

1.8 

2.8 
4.8 
4.8 
4.5 
5.9 
7.9 
4.3 

0.4 
1.2 

40.1 
49.2 
30.4 
17.1 
32.7 
40.1 
16.9 

11.6 
34.6 
32.4 

10.2 
19.8 
19.1 
18.9 
7.1 

43.4 
46.9 
37.3 
51.7 
40.9 
40.1 
46.4 

36.3 
38.6 

0.6 
1.8 
1.9 

29.0 
7.0 
2.8 
12.2 

0.4 
1.2 
0.7 

0.5 
0.8 
0.6 
1.0 
0.2 

1.4 
1.4 
2.0 
1.3 
1.2 
1.5 
1.5 

0.4 

0.8 

Buckwheat      

Flaxseed     

Linseed  meal  (old  process)  . 
Linseed  meal  (new  process) 
Cotton-seed  meal      .... 
Coarse  Fodders 
Fodder  corn  (green)    .     .     . 
Fodder  corn  (field  cured) 
Corn  stover  (field  cured)  .     . 
Fresh  Grass 
Pasture  grasses  (mixed)  .     . 
Kentucky  blue  grass     .     .     . 
Timothy,  different  stages 
Oat  fodder  

Hay 
Timothy 

Redtop   

Kentucky  blue  grass    .     .     . 
Hungarian  grass      .... 

Rowen  (mixed)  

Oat  hay                    .... 

Straw 
Wheat    .              

Oat     

APPENDIX 


149 


DIGESTIBLE   NUTRIENTS  IN   FODDERS  -  Concluded 


NAME  OP  FEED 

DRY 
MATTER 

IN 

100  LB. 

DIGESTIBLE  NUTRIENTS 
IN  100  LB. 

PROTEIN 

CARBOHY- 
DRATES 

ETHER 
EXTRACT 

Fresh  Legumes 
Red  clover,  different  stages  . 

29.2 
25.2 
19.1 

84.7 
78.8 
90.3 
91.6 
89.3 

20.9 

21.1 
13.5 
9.1 
11.4 
11.4 

9.1 
10.2 
12.8 
9.6 
9.4 
9.9 
6.6 

2.9 
2.7 
2.4 

6.8 
5.7 
8.4 
11.0 
16.8 

0.9 

0.9 
1.1 
1.1 
1.0 
0.8 

1.0 
0.6 
3.6 
3.1 
2.9 
3.9 
0.8 

14.8 
13.1 
13.9 

35.8 
32.0 
42.5 
39.6 
38.6 

11.3 

16.3 
10.2 
5.4 
8.1 

7.8 

5.8 
7.3 
4.9 
4.7 
5.2 
4.0 
4.7 

0.7 
0.6 
0.5 

1.7 
1.9 
1.5 
1.2 
1.1 

0.7 

0.1 
0.1 
0.1 
0.2 
0.2 

0.3 

3,7 
0.8 
0.3 
1.1 
0.3 

Legumes 
Red  clover,  medium     .     .    . 
Red  clover,  mammoth      .     . 
Alsike  clover  
Alfalfa  

Silage 
Corn  

Roots  and  Tubers 
Potato    

Mangel  beet    

Rutabaga   
Carrot    „ 

Miscellaneous 
Pumpkin  (field)  .     .     .    «    . 

Cow's  milk      

Skim  milk  (gravity)    .     .     . 
Skim  milk  (centrifugal)  .     . 
Buttermilk 

Whey     

150 


DAIRY  CHEMISTRY 


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APPENDIX  151 

REVIEW   QUESTIONS 

CHAPTER  I 

1.  What  are  the  milk  solids,  and  how  are  they  obtained  ? 
2.  Of  what  compounds  are  the  milk  solids  composed  ?  3.  Give 
the  approximate  percentage  amounts  in  which  these  compounds 
are  present.  4.  What  is  milk  serum?  5.  To  what  extent  does 
the  solid  matter  in  milk  vary  ?  6.  How  much  water  does  aver- 
age milk  contain?  7.  What  are  the  fat  globules  of  milk  ? 
8.  Why  are  they  globular  in  form?  9.  To  what  extent  do 
the  globules  in  milk  vary  in  size  and  number  ?  10.  Are  the  fat 
globules  surrounded  by  a  membrane  ?  11.  What  breeds  pro- 
duce milk  containing  the  largest  fat  globules?  12.  What  is 
casein?  13.  In  what  dairy  operations  does  it  take  the  most 
important  part?  14.  What  is  albumin,  and  how  can  it  be  ob- 
tained from  rnilk?  15.  What  is  milk  sugar?  16.  How  does 
it  resemble  and  how  does  it  differ  from  ordinary  sugar? 
17.  What  is  the  ash  of  milk?  18.  Of  what  is  it  composed? 
19.  How  is  the  ash  of  milk  obtained?  20.  To  what  extent  do 
different  milks  vary  in  composition?  21.  What  is  the  most 
variable  ingredient  in  milk?  22.  Why  should  the  quantity  of 
milk  be  considered  jointly  with  its  percentage  composition  ? 
23.  How  can  the  total  yield  of  fat  and  other  compounds  of 
milk  be  determined?  24.  How  does  the  first  or  fore  milk 
differ  from  the  strippings?  25.  What  are  the  solids  not 
fat  ?  26.  To  what  extent  do  they  vary  in  different  milks  ? 

CHAPTER  II 

27.  What  is  the  object  of  testing  milks?  28.  What  method 
is  most  generally  used  in  milk  testing?  29.  What  can  you  say 
of  the  reliability  of  this  method?  30.  How  should  a  sample 
of  milk  be  taken  from  a  can  or  pail?  31.  What  treatment 
should  milk  in  the  sample  bottle  receive  before  measuring  with 
the  pipette  ?  32.  Why  is  careful  sampling  of  the  milk  neces- 


152  DAIRY  CHEMISTRY 

sary?  33.  What  is  the  pipette?  34.  How  is  milk  meas- 
ured with  the  pipette  ?  35.  How  much  milk  does  the  pipette 
deliver?  36.  What  is  the  test  bottle?  37.  How  is  the 
scale  made  to  read  ?  38.  How  would  you  measure  acid  and 
pour  it  into  the  test  bottle?  39.  After  adding  the  acid,  what 
is  the  next  step  in  the  test?  40.  How  is  the  test  completed? 
41.  How  is  the  fat  read?  42.  What  precautions  should  be 
taken  in  reading  the  fat?  43.  What  causes  some  tests  to 
show  particles  of  casein  below  the  fat  in  the  test  bottle  ?  44. 
Why  are  some  tests  black  or  charred?  45.  How  would  you 
determine  whether  a  test  bottle  is  correctly  graduated  or  not? 
46.  Why  is  it  necessary  to  have  accurately  graduated  test  bot- 
tles? 47.  What  causes  the  separation  of  the  fat  in  the  test? 
48.  In  the  handling  of  the  acid  what  precautions  are  to  be 
observed?  49.  How  can  the  machine  be  speeded ?  50.  Why 
should  the  number  of  revolutions  per  minute  vary  with  the 
diameter  of  the  machine?  51.  What  is  a  composite  sample? 
52.  What  material  is  used  for  its  preservation  ?  53.  How 
long  should  the  composite  sample  be  kept?  54.  What  is  a 
convenient  way  for  handling  and  measuring  the  preservative  ? 
55.  What  kind  of  bottles  should  be  used  for  the  composite 
sample?  56.  How  is  skim  milk  tested ?  57.  How  is  the  fat 
content  in  skim  milk  read?  58.  What  effect  does  partial 
freezing  have  upon  the  composition  of  milk?  59.  How 
should  the  glassware  used  in  making  the  test  be  cleaned? 

60.  What  kind  of  water  should  be  used  in  making  the  test? 

61.  Why  are  some  waters  objectionable  ?       62.   What  are  some 
of  the  necessary  precautions  to  take  in  milk  testing? 

CHAPTER  III 

63.  Of  what  are  the  fat  globules  of  milk  composed?      64. 
What   are  the  three  elements  of  which  fats  are  composed  ? 

65.  Name    the  different  fats  of    which  butter  is  composed. 

66.  To  what  extent  are  these  fats  present?       67.    Name  the 
three  classes  into  which  these  fats  may  be  divided.       68.    Give 


APPENDIX  153 

the  characteristics  of  the  principal  fats  of  butter.  69.  Why 
does  butter  differ  in  composition  from  all  other  fats?  70.  What 
is  meant  by  the  glycerine  and  fatty  acid  content  of  fats? 
71.  What  is  meant  by  saponification  of  fats  ?  72.  What  are 
the  volatile  fatty  acids  of  butter?  73.  Why  do  butters  pro- 
duced from  different  creams  vary  in  hardness  and  other  physi- 
cal properties  ? 

CHAPTER   IV 

74.  What  is  the  lactometer  and  for  what  is  it  used  ?  75. 
What  are  the  lactometer  degrees?  76.  How  is  the  specific 
gravity  of  milk  determined  ?  77.  Why  does  milk  have  a 
higher  specific  gravity  than  water  ?  78.  What  influence 
does  the  removal  of  the  fat  have  upon  the  specific  gravity  of 
milk?  79.  What  influence  does  the  addition  of  water  have 
upon  the  specific  gravity  of  milk?  80.  To  what  extent  do 
changes  of  temperature  influence  the  lactometer  readings  ? 
81.  How  is  skimming  or  watering  of  milk  detected  ?  82.  How 
can  the  Babcock  test  and  the  lactometer  be  used  jointly  in 
milk  testing?  83.  How  are  the  milk  solids  calculated  from 
the  fat  content  and  the  specific  gravity  ?  84.  How  would  you 
determine  the  extent  to  which  milks  have  been  either  watered 
or  skimmed  ? 

CHAPTER  V 

85.  Give  the  physical  properties  of  milk  sugar.  86.  What 
changes  does  milk  sugar  undergo  when  milk  sours  ?  87.  What 
is  produced?  88.  Name  the  conditions  necessary  for  fermen- 
tation of  milk.  89.  What  causes  the  fermentation  to  take 
place  ?  90.  To  what  extent  may  lactic  acid  form  in  milk  ? 
91.  What  causes  milk  to  sour  and  curdle?  92.  How  can  the 
amount  of  lactic  acid  in  milk  be  determined?  93.  Describe 
the  test  employed  for  obtaining  the  acidity  of  milk.  94.  How 
is  the  amount  of  acid  in  the  milk  calculated?  95.  Of  what 
value  is  this  test  in  butter  making  ?  96.  What  per  cent  of 
acidity  should  well-ripened  crearn  show  ? 


154  DAIRY  CHEMISTRY 


CHAPTER  VI 

97.  What  is  cream  ?  98.  To  what  extent  does  it  vary  in 
fat  content?  99.  Give  the  three  ways  in  which  milks  are 
creamed.  100.  How  is  cream  tested?  101.  Why  is  it  more 
accurate  to  weigh  instead  of  measure  the  crearn  used  in  test- 
ing? 102.  What  is  creaming  by  gravity?  103.  To  what 
extent  do  losses  of  butter  fat  occur  in  gravity  creaming? 

104.  How  is  milk  creamed  by  the  cold  deep-setting  process? 

105.  What  are  the  essential  conditions  for  efficient  creaming 
by  this  process?       106.    To  what  extent  do  losses  of  fat  occur 
when  milks  are  creamed  by  the  separator?      107.   How  can 
the  composition  of  separator  cream  be  regulated  ?       108.   What 
should  be  the  temperature  of  milk  when  separated  ?      109.    Why 
should  different  milks  be  separated  at  different  temperatures  ? 
110.   In  what  ways  is  cream  adulterated?      111.   Explain  the 
ripening  process  of   cream.       112.    What  is  the  object  of  the 
ripening  of  cream  ?      113.    Explain  the  workings  of  the  culture 
or  starter.       114.   What  influence  does  delay  have  in  the  grav- 
ity creaming  of  milk  ?       115.   Is  there  any  advantage  in  grav- 
ity creaming  of  mixed  milk?      116.   What  is  cream  raising  by 
dilution?      117.  Is  it  a  desirable  process?      118.   Why? 


CHAPTER  VII 

119.  What  is  churning?  120.  What  changes  take  place  in  the 
form  of  the  fat  globules  during  churning?  121.  What  are 
the  conditions  necessary  for  exhaustive  churning?  122.  Does 
the  ripeness  of  the  cream  affect  churning?  123.  Does  the  fat 
content  of  cream  affect  churning  ?  124.  Why  should  unripened 
mixed  creams  first  be  ripened  before  churning?  125.  Why 
should  the  temperature  of  churning  vary  with  different  creams  ? 
126.  How  would  you  determine  the  best  temperature  for  churn- 
ing ?  127.  What  are  some  of  the  factors  influencing  the  churn- 
ability  of  cream?  128.  At  what  stage  should  churning  be 
stopped?  129.  To  what  extent  should  the  butter  be  washed 


APPENDIX  155 

and  worked?  130.  How  can  the  water  content  of  butter  be 
influenced  by  working?  131.  What  are  the  characteristics  of 
a  good  dairy  salt?  132.  What  is  buttermilk,  and  how  does 
it  compare  in  composition  with  skim  milk  ?  133.  What  be- 
comes of  the  casein  in  butter  making  ?  134.  Of  the  milk  sugar? 
135.  Of  the  albumin  ?  136.  To  what  extent  do  butters  vary 
in  water  content  ?  137.  How  much  fat  does  average  butter 
contain?  138.  How  much  casein  ?  139.  Of  what  are  butter 
colors  composed?  140.  Why  does  one  hundred  pounds  of  fat 
make  more  than  one  hundred  pounds  of  butter?  141.  How 
is  the  butter  yield  estimated  from  the  fat  content  of  milk? 
142.  How  would  you  make  out  a  dividend  in  a  creamery  on  the 
basis  of  the  weight  of  the  milks  and  their  fat  content? 

CHAPTER  VIII 

143.  Define  sanitary  condition  of  milk.  144.  Name  the  fac- 
tors which  influence  the  sanitary  condition  of  milk.  145.  Why 
is  milk  from  diseased  animals  unsanitary  ?  146.  To  what  extent 
do  diseases  affect  the  composition  of  the  milk  ?  147.  How  does 
the  care  of  the  animals  influence  the  sanitary  condition  of  the 
milk  ?  148.  Why  should  the  utmost  cleanliness  be  practiced 
in  the  handling  of  milk?  149.  What  are  the  most  frequent 
causes  of  contaminated  milk?  150.  Why  should  milk  not  be 
left  in  stables?  151.  What  causes  the  difference  in  the  bac- 
terial content  of  milk?  152.  Why  should  stables  be  well 
ventilated?  153.  How  do  unclean  dairy  utensils  foul  milk? 
154.  How  should  pails  and  cans  be  washed  ?  155.  What  effect 
does  the  storing  of  milk  in  unclean  milk  rooms  have  upon  its 
wholesomeness?  156.  In  what  ways  does  the  water  supply 
influence  the  quality  of  the  milk?  157.  What  is  colostrum 
milk,  and  how  does  it  differ  in  composition  from  other  milk? 
158.  What  is  tyrotoxicon?  159.  How  is  it  produced  in 
milk?  160.  What  is  fibrin?  161.  What  gases  are  present 
in  milk?  162.  To  what  is  the  color  of  milk  due ?  163.  How 
would  you  pick  out  milks  of  the  highest  sanitary  value  'I 


156  DAIRY   CHEMISTRY 

164.   How  may  milks  be  the  cause  of  the  spread  of  contagious 
diseases? 

CHAPTER   IX 

165.  What  milk  solids  are  recovered  in  cheese  making? 
166.  What  are  the  proteids  of  milk?  167.  Howdotheproteids 
differ  in  composition  from  the  fats?  168.  In  what  condition  is 
the  casein  in  milk  ?  169.  What  causes  coagulation  of  the  casein  ? 

170.  Is  milk  albumin  recovered  in  ordinary  cheese  making  ? 

171.  What  is  rennet?       172.    How  is  it  obtained ?      173.   For 
what  is  it  used?       174.   What  action  does  it  have  upon  milk? 
175.    What  is  the  rennet  test  and  how  is  it  made  ?       176.   What 
is  the  object  of  this  test  ?       177.    Describe  briefly  the  process  of 
cheddar  cheese  making.       178.   Why  is  it  called  the  cheddar 
process?       179.    How  does  it  differ  from  the  stirred  curd  pro- 
cess?      180.    To  what  is  the  curing  of  cheese  due?       181.   What 
are  the  enzymes?       182.    What  part  do  they  take  in  cheese  ripen- 
ing?      183.   What  is  the  cold  curing  process  ?       184.   What  is 
gained  by  this  process  of  curing  cheese  ?       185.   What  relation- 
ship exists  between  the  fat  content  and  the  cheese  yield  of 
milk  ?      186.    How  can  the  fat  content  of  cheese  be  determined  ? 
187.    How  much  fat  should  cheese  contain?      188.    How  much 
casein?       189.    How  are  dividends,  made  out  in  a  cheese  factory 
on  the  basis  of  the  fat  content  ?       190.    Is  this  an  equitable  basis 
for  making  out  dividends?       191.   How  may  the  approximate 
cheese  and  butter  yield  of  milks  be  determined?       192.   What 
are  some  of  the  kinds  of  cheese  occasionally  manufactured? 
193.    How  is  a  long-keeping  export  cheese  made?       194.    How 
is  a  quick-ripening  or  home-market  cheese  made?       195.    What 
is  the  hot-iron   test,  and  how  is  it  used  in   cheese  making? 
196.    How   do   the   losses   of   fat  in   cheese   making  compare 
with  the  losses  in  butter  making?       197.   Can  rich  milks  be 
made   into   cheese   economically?        198.    How   does    the   fat 
content   of   milk   affect   the  quality  of   cheese?       199.   When 
milk  curdles,  what  becomes  of  part  of  the  lactic  acid  that  is 
formed  ? 


APPENDIX  157 


CHAPTER   X 

200.  What  are  the  by-products  of  milk?  201.  What  are 
the  principal  compounds  in  skim  milk  ?  202.  To  what  does 
skim  milk  owe  its  feeding  value  ?  203.  How  does  skim 
milk  compare  in  feeding  value  with  corn  and  other  grains? 
204.  What  is  the  best  proportion  to  feed  skim  milk  with 
grain  ?  205.  Why  should  separator  slime  be  kept  out  of 
skim  milk?  206.  What  is  the  difference  between  separator 
skim  milk  and  skim  milk  obtained  by  the  gravity  process? 

207.  How  does  whey  differ  in  composition  from  skim  milk? 

208.  How  does  whey  compare  in  feeding  value  with  skim  milk 
and   grains?      209.    What   fertilizer    value    do   the   milk    by- 
products possess?      210.    Why  is  there  but  little  loss  of  fertil- 
ity from  the  farm  in  dairying?      211.    Why  should  skim  milk, 
buttermilk,  and  whey  be  handled  in  the  most  cleanly  way? 

CHAPTER   XI 

212.  What  is  oleomargarine?  213.  Butterine?  214.  How 
are  these  materials  made?  215.  To  what  extent  do  they 
resemble  butter?  216.  How  do  they  differ  from  butter? 
217.  What'  simple  methods  can  be  employed  for  detecting 
oleomargarine?  218.  What  is  renovated  butter  and  how  is 
it  made?  219.  How  does  it  differ  from  other  butter? 
220.  In  what  ways  may  cheese  be  adulterated  ?  221.  In 
addition  to  skimming  and  watering  in  what  other  ways  may 
milks  be  adulterated?  222.  Why  do  medical  authorities 
object  to  the  use  of  preservatives  in  milk?  223.  What  other 
methods  are  sometimes  used  in  testing  milks?  224.  Which 
of  these  methods  are  unreliable  ?  225.  AVhy  are  dairy  laws 
enacted?  226.  What  is  gained  by  inspection  of  dairy  products? 

CHAPTER   XII 

227.  Why  are  market  milks  so  variable  in  character? 
228.  To  what  extent  does  milk  or  cream  vary  in  composition 


158  DAIRY  CHEMISTRY 

during  transportation?  229.  What  is  Pasteurized  milk? 
230.  How  is  milk  Pasteurized?  231.  What  is  sterilized  milk, 
and  how  does  it  differ  from  Pasteurized  milk?  232.  Could 
cream  used  for  butter-making  purposes  be  Pasteurized  to 
advantage?  233.  How  could  milk  be  Pasteurized  on  a  small 
scale  for  home  use  ?  234.  What  is  condensed  milk  ? 

CHAPTER  XIII 

235.  What  relationship  exists  between  milk  secretion  and 
food  supply?  236.  To  what  extent  can  the  per  cent  of  fat  in 
milk  be  increased  by  the  food?  237.  What  is  the  result  of  the 
tests  where  fats  were  fed  in  large  amounts  to  dairy  cows? 
238.  How  does  feed  affect  the  total  yield  of  milk?  239.  Is 
the  fat  in  milk  formed  from  other  nutrients  than  the  fat  in  the 
food  ?  240.  What  effect  on  the  quality  of  butter  does  cotton- 
seed meal  have  when  fed  to  cows  in  large  amounts?  241.  What 
influence  does  corn  alone  and  in  large  amounts  have  upon  the 
quality  of  the  butter?  242.  When  corn  or  cotton-seed  meal  are 
combined  with  other  grains,  what  is  the  effect  on  the  quality  of 
the  butter  ?  243.  When  cows  are  fed  large  amounts  of  linseed 
meal,  what  quality  of  butter  is  produced?  244.  What  effect 
does  gluten  meal  have  upon  the  quality  of  the  butter? 

245.  When   oats   are   fed,  what  kind  of  butter  is  produced? 

246.  What  effect  do  the  wheat  by-products   have  upon   the 
butter?      247.   To  what  extent  do  farm  grains  differ  in  milk- 
producing  power  in  mixed  rations?      248.  What  coarse  fodders 
produce  the  best  quality  of  milk?      249.    What  effect  do  over- 
ripe and  fibrous  fodders  have  upon  the  quality  of  the  milk  and 
butter?       250.   Does  silage  exert  a  favorable  influence  upon 
the  character  of  the  butter?      251.    To  what  is  silage  odor  in 
milk   largely  due?      252.   How  do  turnips,  rape,  and  onions 
affect  the  flavor  of   milk?       253.   To  what  are  the   desirable 
flavors    in    milk   due?      254.    What    causes  the    undesirable 
flavors?      255.    Why   does   a   balanced    ration  produce   dairy 
products  of   the  best  quality?      256.    Under  what  conditions 


APPENDIX  159 

are  abnormal  milks  and  dairy  products  produced  ?  257.  Are 
there  any  foods  that  exert  a  marked  ability  to  cause  an  increase 
in  milk  secretion  ?  258.  How  do  so-called  stock  foods  affect 
milk  yield?  259.  Under  what  conditions  of  feeding  are  the 
best  returns  in  milk  yield  and  quality  of  product  secured? 
260.  Why  is  liberal  feeding  necessary  to  produce  prolonged 
milk  secretion?  261.  To  what  extent  do  individual  animals 
differ  in  their  ability  to  utilize  foods  for  milk  production  ? 
262.  What  factors  influence  milk  secretion  ?  263.  To  what 
extent  can  the  secretion  of  milk  be  influenced  ? 


CHAPTER   XIV 

264.  What  uses  are  made  of  the  food  by  the  body  ?  265.  Do 
all  the  nutrients  of  the  food  serve  the  same  purpose  ?  266.  What 
is  a  nutrient?  267.  Into  what  two  classes  of  nutrients  are 
the  compounds  of  foods  divided?  268.  What  is  the  differ- 
ence in  composition  between  these  two  classes  of  nutrients? 
269.  Which  class  of  nutrients  is  found  in  smaller  amounts 
in  food  stuffs?  270.  Which  class  is  the  more  expensive? 
271.  Give  an  example  of  each  class.  272.  What  is  the  crude 
protein?  273.  What  are  the  carbohydrates?  274.  What 
is  dry  matter?  275.  How  is  it  obtained?  276.  To  what 
extent  does  the  water  content  of  foods  vary?  277.  Define 
ash  or  mineral  matter.  278.  To  what  extent  is  ash  present 
in  grains?  279.  What  compounds  are  present  in  plant 
ash?  280.  What  is  organic  matter,  and  how  is  it  obtained? 
281.  What  functions  do  the  proteids  of  food  serve?  282. 
Why  should  foods  contain  a  fairly  liberal  supply  of  proteids  ? 
283.  What  is  the  result  when  the  food  contains  too  scant  an 
amount  of  proteids?  284.  Why  are  abnormal  amounts  of 
proteids  in  foods  objectionable?  285.  What  is  the  object 
of  the  rational  feeding  of  animals?  286.  What  functions 
do  the  carbohydrates  of  foods  serve  ?  287.  Do  carbohydrates 
found  in  different  food  materials  have  the  same  general  com- 
position? 288.  What  are  some  of  the  carbohydrates  found 


160  DAIRY  CHEMISTRY 

in  food  stuffs?  289.  What  is  crude  fiber,  and  how  is  it  ob- 
tained? 290.  To  which  of  the  two  large  classes  of  compounds 
found  in  food  stuffs  does  crude  fiber  belong?  291.  What  is 
crude  fat,  and  why  is  it  sometimes  called  ether  extract? 
292.  How  does  fat  as  a  nutrient  compare  with  starch  in 
heat-producing  power  ?  293.  What  are  digestible  nutri- 
ents? 294.  How  are  they  obtained?  295.  What  is  the 
caloric  value  of  a  ration  ?  296.  What  is  the  nutritive  ratio  ? 
297.  What  is  a  wide  ration?  298.  What  is  a  narrow  ra- 
tion? 299.  On  what  basis  should  the  foods  for  the  dairy 
be  selected?  300.  How  do  farm  grains  compare  in  milk- 
producing  power  with  average  mill  products  other  than  oil- 
seed products?  301.  Name  the  coarse  fodders  most  suitable 
for  dairy  feeding.  302.  How  should  the  amount  of  grain 
which  an  animal  receives  be  regulated?  303.  How  much 
coarse  fodder  should  a  cow  receive?  304.  How  much  grain 
should  a  cow  yielding  twenty-eight  pounds  of  milk  receive? 
305.  Give  the  amount  of  nutrients  which  should  be  present 
in  the  ration  of  a  dairy  cow.  306.  How  is  a  ration  for  a 
dairy  animal  calculated?  307.  How  would  you  determine 
whether  a  ration  conformed  sufficiently  to  a  standard  ration? 
308.  How  would  you  determine  when  it  is  desirable  to  use 
one  grain  in  a  ration. in  large  amounts  in  preference  to  an- 
other ?  309.  How  would  you  calculate  the  amount  of  digesti- 
ble nutrients  which  can  be  purchased  for  $1.00  when  grains  are 
at  different  prices?  310.  In  selecting  grains,  to  what  nutrient 
should  the  preference  be  given?  311.  In  case  there  is  only 
a  small  difference  in  the  amount  of  this  nutrient  which  can  be 
purchased  for  $1.00,  then  what  nutrient  should  be  taken  as  the 
basis?  312.  Why  is  it  possible  for  two  farmers  to  feed  the 
same  kinds  of  grains  and  coarse  fodders  and  yet  secure  entirely 
different  returns  in  milk  yields?  313.  In  order  to  secure  the 
best  returns  in  milk  yields  from  the  food  consumed,  why  should 
the  animals  be  cared  for  under  the  most  sanitary  conditions? 
314.  Why  should  grains  be  weighed  when  fed  ?  315.  To  what 
extent  do  gi'ains  and  mill  products  vary  in  bulk  and  weight? 


APPENDIX  161 


REFERENCES 

THE  references  given  in  the  following  pages  are  not  intended 
to  represent  a  complete  bibliography  of  the  subject.  The  stu- 
dent is  advised  to  consult  some  of  the  bulletins  and  articles 
referred  to  so  as  to  obtain  more  information  upon  many  of  the 
topics  that  are  only  briefly  discussed  in  this  work.  It  has  not 
been  possible  to  give  the  references  and  authorities  for  each 
statement  that  has  been  made  in  this  book,  or  in  those  cases 
where  different  and  conflicting  views  ai-e  held,  to  enter  into 
discussion  of  questions.  The  literature  of  dairying  is  very 
extensive,  and  there  are  a  number  of  works  that  treat  of 
special  topics,  as:  Testing  Milk  and  its  Products,  by  Woll  and 
Farrington ;  Dairy  Chemistry,  by  Richmond ;  Dairy  Bacteriol- 
ogy,  by  Russell;  Milk  and  its  Products,  by  Wing;  Feeds  and 
Feeding,  by  Henry  ;  and  Feeding  of  Farm  Animals,  by  Jordan. 
These  should  be  frequently  consulted  in  studying  the  subject. 
The  student  should  early  acquire  the  habit  of  consulting  dif- 
ferent works,  as  many  topics  are  presented  more  clearly  in  one 
than  in  another. 


REFERENCES   TO   CHAPTER   I 

1.  The  Composition  of  Milk.     Konig:  Chemie  der  Mensch- 
lichen  Nahrungs-  und  Genussmittal. 

2.  The  Composition  of  Cow's  Milk.     Blyth  :  Food  Analysis. 

3.  The  Physical  Composition  of  Milk.     Duclaux:  Le  Lait, 
Etudes  Chemiques  et  Microbiologiques. 

4.  The  Composition  of  Milk.      Wisconsin  Experiment  Sta- 
tion, Bulletin  No.  19. 

5.  The  Constitution  of  Milk.    Wisconsin  Experiment  Station, 
Bulletin  No.  18. 

6.  The  Composition  of  Milk  and  its  Products.     Richmond : 
Analyst,  August,  1894. 

7.  The  Composition  of  Milk  as  affected  by  Change  of  Milkers 


162  DAIRY  CHEMISTRY 

and  Change  of  Quarters.     Wisconsin  Experiment  Station  Re- 
port, 1889. 

8.  Variations  in  the  Fat  Content  of  Milk.     Weilandt :  Milch 
Zeitung,  24  (1895). 

9.  The  Average  Composition  of  Milk.     Vieth :  Analyst,  18, 
192,  193. 

10.  Historical  Article  regarding  Milk.    Blyth:  Food  Analysis. 

11.  The  Composition  of  Milk  from  Different  Breeds.    Michi- 
gan Experiment  Station,  Bulletin  No.  68. 

12.  The  Composition  of  Milk  from  Different  Breeds.     New 
York  State  Station  Report,  1891. 

13.  The  Composition  of  Milk.     Maine  Experiment  Station 
Reports,  1890,  1893. 

14.  Variations  in  Milk  during  the  Period  of  Lactation.    Ver- 
mont Experiment  Station,  Sixth  Annual  Report. 

15.  Composition  of  Milk.      Wisconsin  Experiment  Station 
Report,  1889  ;  also  Bulletins  Nos.  15  and  16 ;  also  Fifth  Annual 
Report. 

16.  Composition  of  Milk.     New  Jersey  Experiment  Station, 
Bulletins  Nos.  61,  65,  68,  77. 

17.  Composition  of  Milk.     Massachusetts  State  Station  Re- 
ports, 1888,  1889,  1890,  1891,  1892. 

18.  The  Number  and  Size  of  Fat  Globules  in  Milk.     AVis- 
consin  Experiment  Station  Report,  1890. 

19.  The  Fat  Globules  of  Milk.     Maine  Experiment  Station, 
Annual  Report,  1890. 

20.  Conditions  influencing  the  Number  and  Size  of  the  Fat 
Globules.     Milch  Zeitung,  24  (1895). 

21.  On  the  Variation  in  the  Number  and  Size  of  Fat  Glob- 
ules.    Pennsylvania  Experiment  Station  Report,  1895. 

22.  The  Size  of  Fat  Globules  in  Milk.    Vermont  Experiment 
Station,  Fourth  Annual  Report. 

23.  Size  of  Fat  Globules  in  the  First  and  Last  Half  of  Milk- 
ing.    Indiana  Experiment  Station,  Bulletin  No.  24. 

24.  The  Size  of  Fat  Globules  in  Milk  of  Cows  of  Different 
Breeds.  New  York  State  Experiment  Station  Reports,  1891, 1892. 


APPENDIX  163 

25.  Composition  of  First  Milk  and  Strippings.     Connecticut 
State  Experiment  Station  Report,  1886. 

26.  Fore  Milk  and  Strippings.     Blyth  :  Food  Analysis. 

27.  Relation  of  Fat  and  Casein  in  Milk.     Vermont  Experi- 
ment Station,  Fourth  Annual  Report. 

28.  Liquid  Condition  of  the  Fat.    Soxhlet :  Landwirtschaft- 
lischen  Versuchs-Stationen,  1876. 

29.  No  Membrane  about  Milk  Fat  Globules.     Martiny :  Die 
Milch. 

30.  Artificial  Emulsions  representing  Milk.     Duclaux :  An- 
nales  de  1'Institut  Nat.  agronomique,  1882. 

31.  The  Membrane  of  the  Milk  Fat  Globule.     Jurstenburg  : 
Die  Milch  drusen  die  Kuh. 

32.  The  Membrane  of  the  Fat  Globule.     Bechamp :  Comptes 
Rendus,  1888. 

33.  Composition  of  the  Ash  of  Milk.     Maine   Experiment 
Station  Report,  1890. 

34.  Milk  Ash  Analysis.     New  Hampshire  Experiment  Sta- 
tion Report,  1888. 

35.  Average  Composition  of  Milk  Ash.     Konig :  Chemische 
der  menschlichen  Nahrungs-  und  Genussmittel.     Band  IT. 

36.  The   Phosphates   of  Milk.     Duclaux:    Annals   Pasteur 
Institute,  1893. 

37.  Calcium  Phosphate  and  the  Casein.     Soldner :  Die  Land- 
wirtschaftlichen  Versuchs-Stationen,  1888,  35. 

38.  Yield  of  Front  and  Rear  Udder  of  Cow.     Wis.Rept.,  1898. 

39.  The  Milk  Yield  of  Quarters  on  Same  Side  of  Udder. 

40.  The  Composition  of  Frozen  Milk.     Wisconsin  Station, 
Twentieth  Annual  Report. 

41.  The  Fat  Globules  of  Cows'  Milk.     Wisconsin  Station, 
Twentieth  Annual  Report. 

42.  On  the  Average  Composition  of  Milk  of  Pure-bred  Cows  of 
Different  Breeds.  Wisconsin  Station,  Twentieth  Annual  Report. 

43.  On  the  Average  Composition  of  Milk  of  Pure-bred  Cows 
of  Different  Breeds.     Wisconsin  Station,  Eighteenth  Annual 
Report. 


it>4  DAIRY  CHEMISTRY 

44.   Variations  in  Milk  and  Milk  Production.     Illinois  Ex- 
periment Station,  Bulletin  No.  51. 

REFERENCES   TO   CHAPTER   II 

1.  The  Babcock  Test.     A  New  Method  for  the  Estimation 
of  Fat  in  Milk,  especially  adapted  to  Creameries  and  Cheese 
Factories.     Wisconsin  Experiment  Station,  Bulletin   No.  24 ; 
also  Annual  Report,  1890. 

2.  Babcock  Test.     Notes  on  its  Use  and  the  Lactometer. 
Wisconsin  Experiment  Station,  Bulletin  No.  31. 

'  3.  Application  of  Dr.  Babcock's  Centrifugal  Method  to  the 
Analysis  of  Milk,  Skim-milk,  etc.  Cornell  University  Experi- 
ment Station,  Bulletin  No.  29. 

4.  New  Points  in  Manipulation  of  the  Babcock  Test.     Illi- 
nois Experiment  Station,  Bulletin  No.  27. 

5.  The  Babcock  Test.     Association  of  Official  Agricultural 
Chemists'  Report,  1890. 

6.  The  Babcock  Method  of  finding  the  Amount  of  Butter-fat 
in  Milk.     Connecticut  State  Experiment  Station,  Bulletin  No. 
106 ;  also  Reports,  1891,  1894. 

7.  Directions  for  using  the  Babcock  Milk  Test.     Pennsyl- 
vania Experiment  Station,  Bulletin  No.  33,  Report,  1895. 

8.  The  Babcock  Method  of    Milk  Analysis.     F.  T.  Shutt: 
Analyst,  17,  200 ;  Chemical  News,  64,  4. 

9.  Accuracy  of  the  Babcock  Milk  Test.     Cornell  University 
Experiment  Station,  Bulletin  No.  25. 

10.  Accuracy  of  the  Babcock  Milk  Test.     Illinois  Experi- 
ment Station,  Bulletin  No.  14. 

11.  Comparative  Trials  of  the  Babcock  Milk  Test.     Hein- 
rich :  Molkerei  Zeitung,  1893,  No.  4. 

12.  The  Babcock  Test.  Wiley :  Agricultural  Analysis,  Vol.  III. 

13.  Marking  Test-bottles.     Illinois  Agricultural  Experiment 
Station,  Bulletin  No.  18. 

14.  Milk  Sampling.     Delaware  Experiment  Station,  Bulletin 
No.  31. 


APPENDIX  165 

15.  The  Testing  of  Milk.     North  Carolina  Experiment  Sta 
tion,  Bulletin  No.  113. 

16.  Composite  Milk  Samples.     Patrick  :  Journal  of  Analyti- 
cal and  Applied  Chemistry,  5,  8. 

17.  The  Composite  Test.     Wisconsin  Experiment  Station, 
Bulletin  No.  36. 

18.  Composite  Sampling  of  Milk.   Iowa  Experiment  Station, 
Bulletins  Nos.  9,  14,  and  22. 

19.  Composite  Method  of  Milk  Sampling.     Illinois  Experi- 
ment Station,  Bulletins  Nos.  16  and  18. 

20.  Method  of  Sampling  Milk  for  Analysis.     Pennsylvania 
Experiment  Station,  Annual  Report,  1892. 

21.  Preservatives  for  Milk  Samples.     Iowa  Experiment  Sta- 
tion, Bulletin  No.  11. 

22.  Milk  Sampler.     Wiley  :    Agricultural  Analysis,  Vol.  III. 

23.  The  Trowbridge  Method  of  Calibrating  Babcock  Test- 
bottles.     Wisconsin   Experiment  Station,  Eighteenth   Annual 
Report. 

24.  Methods    and   Apparatus  for   testing    Milk    and   Milk 
Products.     Wisconsin  Experiment  Station,  Twentieth  Annual 
Report. 

25.  Examination  of  Babcock  Apparatus.     Connecticut  Ex- 
periment Station,  Report  1901,  Part  IV. 

26.  Testing  Dairy  Products  by  the  Babcock  Test.     Maine 
Experiment  Station,  Report  of  1897. 

27.  The  Babcock  Test.     New  Hampshire  Experiment  Sta- 
tion, Bulletin  No.  114. 

28.  Inspection  of   Babcock   Milk  Test-bottles.     New  York 
Experiment  Station,  Bulletin  No.  178. 


REFERENCES   TO   CHAPTER   IV 

1.  Table  for  Corrections  of  the  Temperature  in  Lactometry 
(Centigrade  Scale).  Konig:  Untersuchungen  in  landwirt- 
schaftlich  und  gewerblich  Wichtiger  Stoife. 


166  DAIRY  CHEMISTRY 

2.  A  Simple  Formula  for  calculating  the  Solids  not  Fat. 
Babcock :  Wisconsin  Experiment  Station,  Bulletin  No.  34. 

3.  The  Adulteration  of  Milk.     Blyth :  Foods ;  Composition 
and  Analysis. 

4.  Comparison  of  Results  by  the  Use  of  the  Formulas  of 
Hehner  and  Richmond,  Fleischmann,  and  Babcock,  with  the 
Gravimetric  Method.    Report  of  the  Eighteenth  Annual  Conven- 
tion of  the  Association  of  Official  Agricultural  Chemists,  1894. 

5.  Effect  upon  the  Specific  Gravity  of  Milk  by  allowing  the 
Milk  to  stand  after  Milking.    Richmond :  Report  of  Eighteenth 
Annual    Convention  of   Association    of    Official   Agricultural 
Chemists,  1894. 

6.  Lactodensimeter.     Quevenne-MUller :   Grandeau,  Analyse 
des  Materies  Agricoles. 

7.  The  Adulteration  of  Milk.     Various  articles  in  the  current 
numbers  of  the  Analyst. 

8.  Legal  Cases  relating  to  the  Adulteration  of  Milk.   Various 
and  numerous  articles  in  the  current  numbers  of  the  Milch 
Zeitung. 

REFERENCES  TO  CHAPTER  V 

1.  Influence  of  Sugar  on  the  Nature  of  the  Fermentation 
occurring  in  Milk  and  Cheese.    Wisconsin  Experiment  Station, 
Eighteenth  Annual  Report. 

2.  Galactase,  the  Inherent  Digestive  Enzyme  of  Milk.     Wis- 
consin Experiment  Station,  Twentieth  Annual  Report. 

3.  Milk  Fermentations.     United  States  Department  of  Agri- 
culture, Farmers'  Bulletins  Nos.  9  and  29,  also  current  numbers. 

4.  Dairy  Bacteriology.     United  States  Department  of  Agri- 
culture, Office  of  Experiment  Stations,  Bulletin  No.  25. 

5.  The  Number  of  Bacteria  in  Milk.     (Storrs)  Connecticut 
Experiment  Station,  Seventh  Annual  Report. 

6.  Bacteria  in  their  Relation  to  the  Dairy.     Lugger:  Minne- 
sota Experiment  Station,  Annual  Report,  1893. 

7.  Ripening  of  Cream  and  Milk  Fermentations.     Article  in 
Handbook  of  Experiment  Station  Work. 


APPENDIX  167 

8.  The   Action  of  Different  Classes  of  Bacteria  on  Milk. 
Adametz  :  Monatsschrifte  fur  Thierheilkunde,  1890. 

9.  Bacteria  in  the  Dairy.      Conn  :  (Storrs)  Connecticut  Ex- 
periment Station,  Third,  Fourth,  Fifth,  Sixth,  Seventh,  and 
Eighth  Annual  Reports. 

10.  Milk  Sugar.     Rein  sen  :  Organic  Chemistry. 

11.  An  Acid  Test  of  Cream.     Illinois  Experiment  Station, 
Bulletin  No.  32. 

12.  The  Alkaline  Tablet  Test  of  Acidity  in  Milk  or  Cream. 
Wisconsin  Experiment  Station,  Bulletin  No.  52. 

13.  Lactic  Acid  Ferments.     Pasteur:   Studies  on  Fermen- 
tation. 

14.  Outlines  of  Dairy  Bacteriology.     Russell. 

15.  Le   Lait,  Etudes  Chemiques  et  Microbiologiques.     Du- 
claux. 

16.  Determining  the  Acid  in  Milk.     Hopkins  and  Powers: 
Report  of  the  Association  of  Official  Agricultural  Chemists, 
1895. 

REFERENCES   TO   CHAPTER   VI 

1.  Ripening   Cream  with   Pure   Cultures.      Conn :  (Storrs) 
Connecticut  Experiment   Station,    Fifth,  Sixth,  and    Seventh 
Annual  Reports. 

2.  Ripening  of   Cream  with  Artificial  Cultures.     Adametz: 
Landvvirtschaftlichen  Versuchs-Stationen,  1892. 

3.  Artificial  Butter  Cultures.     Storch  :  Milch  Zeitung,  1890. 

4.  Artificial  Butter  Cultures.     Weigmann  :  Milch  Zeitung, 
1890. 

5.  Experiments  with  Cream  :  Ripening,  Flavor,  Aroma,  Acid. 
Conn :    (Storrs)    Connecticut    Experiment    Station,    Bulletin 
No.  16. 

6.  Experiments  in  the  Ripening  of  Cream  by  Means  of  Pure 
Cultures.     F.  Fries  and  H.  P.  Lunde  :  reported  in  Experiment 
Station  Record,  7,  No.  3. 

7.  Abnormal  Ripening  of  Cream  due  to  Faulty  Character  of 
Milk.    L.  Adametz :  Milch  Zeitung,  1893,  No.  18. 


168  DAIRY  CHEMISTRY 

8.  Cream   Ripening  with   Pure  Cultures.     Milch   Zeitung. 
Experiment  Station  Record,  7,  No.  1. 

9.  The  Composition  of  Cream.     Massachusetts  Experiment 
Station  Reports,  1889,  1890,  1892,  1893. 

10.  On  the  Raising  of   Cream  on  the  Milk  Route.      Berg- 
mann  :  Milch  Zeitung,  1893. 

11.  Effects  of  Transportation  upon  the  Fat  Content  of  Milk. 
Klein  :  Chemisches  Centralblatt,  89,  397. 

12.  Variations  in  Fat  Content  in  Milk  served  from  Cans  to 
Customers.     Legal  Case.     Analyst,  17,  189. 

13.  Variations  in  Fat  of  Milk  served  to  Customers  in  Dip- 
ping   from    Cans.      Cornell   University  Experiment  Station, 
Bulletin  No.  20. 

14.  Variations   in    the   Fat    of   Milk   served   to   Customers 
from    Milk    Cans.       Ontario    Agricultural    College,   Bulletin 
No.  16. 

15.  Effects  of  Delay  in  Creaming  Milk.     Maine  Experiment 
Station  Report,  1890. 

16.  Effects  of  Delayed  Setting.     Wisconsin  Experiment  Sta- 
tion, Bulletin  No.  29. 

17.  Delay  in  Setting.     See  Creaming  Article  in  Handbook 
of  Experiment  Station  Work. 

18.  Effects  of  Delay  in  Creaming  Milk.     Cornell  University 
Experiment  Station,  Bulletin  No.  29. 

19.  Cream  Raising  by  Dilution.     Cornell  University  Experi- 
ment Station,  Bulletins  Nos.  20  and  29. 

20.  Cream  Raising  by  Dilution.    Illinois  Experiment  Station, 
Bulletins  Nos.  12  and  18. 

21.  Cream  Raising  by  Dilution.     Vermont  Experiment  Sta- 
tion, Fourth  and  Fifth  Annual  Reports. 

22.  Cream  Raising  by  Dilution.     Indiana  Experiment  Sta- 
tion, Bulletin  No.  44. 

23.  Cream  Raising  by  Dilution.     Article,  Creaming  of  Milk, 
in  Handbook  of  Experiment  Station  Work. 

24.  Testing  Cream  and  Milk.     Maine  Experiment  Station, 
Bulletin  No.  4. 


APPENDIX  169 

25.  Testing  Cream  by  the  Babcock  Test.     Connecticut  Ex 
periment  Station  (New  Haven),  Eighteenth  Annual  Report. 

26.  The   Babcock  Test   as   a  Basis  for  Payment  in  Cream- 
gathering  Creameries.     Connecticut  Experiment  Station  (New 
Haven),  Bulletin  No.  119. 

27.  The  Composition  of  Cream.    Konig :  Chemie  der  Mensch- 
lichen  und  Genussmittel,  Band  II. 

28.  Test  of  Cream  Separators.     Cornell  University  Experi- 
ment Station,  Bulletins  Nos.  66  and  105. 

29.  Test  of  Cream   Separators.     Pennsylvania    Experiment 
Station,  Bulletins  Nos.  20  and  21,  Annual  Report,  1895. 

30.  Report   on    Separators,   Gravity,  Creaming,    etc.      Iowa 
Experiment  Station,  Bulletin  No.  25. 

31.  Tests  of   Dairy  Implements.      North  Carolina   Experi- 
ment Station,  Bulletin  No.  114. 

32.  Hand  Power  Cream  Separators.     Delaware  Experiment 
Station,  Bulletin  No.  27,  Fifth  Annual  Report. 

33.  Cream  Raising  by  the  Cold  Deep-setting  Process.     Min- 
nesota Experiment  Station,  Bulletin  No.  19. 

34.  Creaming  of  Milk.     Article  in  Handbook  of  Experiment 
Station  Work. 

35.  Creaming  Experiments.     Babcock:   Wisconsin   Experi- 
ment Station,  Bulletin  No.  29. 

36.  The  Ripening  of  Cream.     Conn  :   (Storrs)   Connecticut 
Experiment  Station,  Report,  1900. 

37.  Commercial  Butter  Cultures.     Pennsylvania  Experiment 
Station,  Bulletin  No.  44. 

38.  Variations  in   Cream  and  Milk  Tests.      South  Dakota 
Experiment  Station,  Bulletin  No.  73. 

39.  Cream  Testing.  Iowa  Experiment  Station,  Bulletin  No.  52. 

40.  A  Modified  Cream  Test  Bottle.     Wisconsin  Experiment 
Station,  Nineteenth  Annual  Report. 

REFERENCES  TO  CHAPTER  VII 

1.  Loss  of  Fat  in  Butter-making.    Iowa  Experiment  Station, 
Bulletin  No.  11. 


170  DAIRY  CHEMISTRY 

2.  Loss  of  Fat  in  Butter-making,  -with  increase  in  Lactation 
Period.     New  York  State  Experiment  Station  Report,  1891. 

3.  Butter  Production    from    Milk  at    Different   Periods  of 
Lactation.     Maine  Experiment  Station  Report,  1889. 

4.  Loss  of  Fat  in  Butter-making.     Article  on  Butter-making 
in  Handbook  of  Experiment  Station  Work. 

5.  Composition  of   the    Slime   from  the   Centrifugal  Bowl. 
Fleischrnann  :    Lehrbuch  der  Milchwirtschaft. 

6.  Butter-making.    Fleischrnann  :   Lehrbuch  der  Milchwirt- 
schaft. 

7.  Churning  and  Butter-making.      Gurler:    American  Dai- 
rying. 

8.  Churning.     Article  in  Handbook  of  Experiment  Station 
Work. 

9.  Churning  Experiments.     Iowa  Experiment  Station,  Bul- 
letin No.  22. 

10.  On  the  Churning  Process  and  the  Formation  of  Butter. 
A.  Jscher  Kasserd:  Milch  Zeitung,  No.  23, 1894. 

11.  The  Churning  Temperature  of  Sweet  and  Sour  Cream. 
New  York  State  Experiment  Station  Report,  1889. 

12.  Tests  of  Box  and  Barrel  Churns.     Vermont  Experiment 
Station,  Bulletin  No.  27. 

13.  The  Acidity  of  the  Cream  and  the  Yield  of  Butter.     Illi- 
nois Experiment  Station,  Bulletin  No.  9. 

14.  Churning  the  Cream  from  Cows  at  Different  Periods  in 
Lactation.     Haecker  :  Hoard's  Dairyman,  1894. 

15.  Butter-making.     Powrian  :    La  laitiere :    Art  de  traiter 
le  lait,  de  fabrique  le  beurre  et  les  principaux  fromages. 

16.  The   Composition  of    Butter.      Minnesota   Experiment 
Station,  Bulletin  No.  19. 

17.  Composition  of  Butter.     Wisconsin  Experiment  Station, 
Annual  Report,  1889. 

18.  Composition  of    Butter.      Massachusetts  State  Station, 
Annual  Report,  1889. 

19.  Composition  of  Butter.     Pennsylvania  Experiment  Sta- 
tion, Annual  Report,  1893. 


APPENDIX  171 

20.  The  Composition  of  Butter.     Connecticut  State  Station, 
Annual  Report,  1892. 

21.  Composition   of    Sweet   Cream  Butter.     West  Virginia 
Experiment  Station,  Annual  Report,  1890. 

22.  Composition  of   Sweet  and  Sour  Cream  Butter.      Iowa 
Experiment  Station,  Bulletin  No.  18. 

23.  The  Composition  of   Butter   from    Different  Countries. 
Konig :  See  reference  No.  6. 

24.  Abnormal  Amounts  of  Water  in  Butter — Legal  Cases. 
Current  numbers  of  the  Analyst. 

25.  The  Yellow  Coloring   Matter   of  Milk.     Blyth:   Foods, 
their  Composition  and  Analysis. 

26.  The  Proteids  of  Butter  in  Relation  to  Mottled  Butter. 
New  York  Experiment  Station  (Geneva),  Bulletin  No.  263. 

27.  Heated  Milk  for  Butter-making.     Pennsylvania  Experi- 
ment Station,  Bulletin  No.  45. 

28.  Paying  for  Separator  Cream  at  the  Creamery.     Vermont 
Experiment  Station,  Bulletin  No.  100. 

29.  Salt   in    Butter.      Iowa   Experiment   Station,   Bulletin 
No.  80. 

30.  Moisture  Content  of  Butter  and  Methods  of  controlling 
it.     Iowa  Experiment  Station,  Bulletin  No.  76. 

31.  Keeping  Qualities  of  Butter.     Iowa  Experiment  Station, 
Bulletin  No.  71. 

32.  Influence  of   Certain    Conditions   in   Churning  on    the 
Amount  of  Water  in  Butter.     Iowa  Experiment  Station,  Bul- 
letin No.  52. 

33.  Effect  of  Salt  and  the  Size  of  Butter  Granules  on  the 
Water   Content  of   Butter.      Wisconsin   Experiment   Station, 
Twentieth  Annual  Report. 

34.  Salt  Crystals  on  the  Surface  of  Butter.     Wisconsin  Ex- 
periment Station,  Twentieth  Annual  Report. 

35.  Score  of  Butter,  as  affected  by  the  Size  of    Package. 
Wisconsin  Experiment  Station,  Twentieth  Annual  Report. 

36.  Composition   of    Dairy    Salt.      Wisconsin    Experiment 
Station,  Twentieth  Annual  Report. 


172  DAIRY  CHEMISTRY 

37.  Calculating  Dividends  for  Milk  and  for  Cream  at  the 
Same  Factory.  Wisconsin  Experiment  Station,  Seventeenth 
Annual  Report. 

REFERENCES   TO   CHAPTER   VIII 

1.  The   Behavior  of  Anthrax   Bacilli   in   Milk.     O.   Caro: 
Chemisches  Centralblatt,  1894,  1,  164. 

2.  Behavior   of   Cholera    Germs    in    Milk.      Heim :    Milch 
Zeitung,  21,  1892. 

3.  Vitality   of   Tuberculosis   Bacilli.      Forster   and   Mann : 
Milch  Zeitung,  22,  1894. 

4.  Tuberculosis  and  Public  Health,  etc.,  Law.     New  York 
Experiment  Station,  Bulletin  No.  65. 

5.  Typhoid    Fever  disseminated  through  the  Milk  Supply. 
Russell :  Science,  November  15,  1895. 

6.  Diseases  conveyed  by  Milk.    B.  Lee  :  Agriculture  of  Penn- 
sylvania, 1894. 

7.  Milk   as  a  Source  of  an   Epidemic  of   Typhoid   Fever. 
Schmidt :  Milch  Zeitung,  23,  1894. 

8.  Danger  from  consuming  the  Milk  of  Sick  Cows.    F.  Baum  : 
Archiv  wissech  und  praktische  Thierheilkunde,  18,  Heft  384. 

9.  On    Ptomaines    in    Milk.      V.    Malenchini :     Zeitschrift 
Nahrungsmittel    Uutersuchen   und   Hygiene. 

10.  The  Care  of  Milk  for  Cheese  Factories  and  Creameries. 
Ontario  Agricultural  College,  Bulletin  No.  44. 

11.  Cleanliness  in  Handling  Milk.     North  Dakota  Experi- 
ment Station,  Bulletin  No.  21. 

12.  Poisonous  Milk  and  Milk  Panics.  Wanklyn  :  Milk  Analy- 
sis. 

13.  Milk    Inspection    affecting    Death    Rate    of    Children. 
Milch  Zeitung,  9,  24,  and  349. 

14.  Citric   Acid   as  a  Normal  Constituent  of  Cow's  Milk. 
Henkel :  Die  Landwirtschaftlichen  Versuchs-Stationen,  39. 

15.  Citric  Acid  in  Milk.     Abstract.     Sixth  Annual  Conven- 
tion (1889),  Association  of  Official  Agricultural  Chemists. 


APPENDIX  173 

16.  The  Composition,  Creaming,  and  Churning  of  Colostrum. 
Vermont  Experiment  Station,  Fifth  Annual  Report. 

17.  Composition    of    Colostrum   Milk.      Kruger :    Molkerei 
Zeitung,  1892. 

18.  The  Chemical  Composition  of  Cow's  Colostrum.     Blyth  : 
Foods,  their  Composition  and  Analysis. 

19.  Nature  of  the  Colostrum  Cells.    Heidenhain :  Handbuch 
der  Physiologic. 

20.  Tyrotoxicon.       Vaughan :     Michigan    State    Board    of 
Health  Report,  1886. 

21.  The  Chemistry  of  Tyrotoxicon,  and  its  Action  on  Lower 
Animals.     Vaughan:  Analyst,  13,  141. 

22.  Fibrin  in  Milk.     Proceedings  of  the  Society  for  the  Pro, 
motion  of  Agricultural  Science,  1888. 

23.  Fibrin  in  Milk,  and  its  Effects  upon  Creaming.     Wiscon- 
sin Experiment  Station,  Bulletin  No.  18. 

24.  Gases  in  Milk.     Kirchner :   Handbuch   der    Milchwirt- 
schaft. 

25.  Gases  in  Milk.     Blyth :  Foods,  their  Composition  and 
Analysis. 

26.  Gas-producing  Organism.    Baumann  :  Molkerei  Zeitung, 
7,  1893. 

27.  Blue  Milk,  Red  Milk,  Brownish  Red  Milk,  Bitter-milk. 
Lugger :  Minnesota  Experiment  Station,  Annual  Report,  1893. 

28.  Creaming  and  Aerating   Milk.     Cornell  University  Ex- 
periment Station,  Bulletin  No.  39. 

29.  Aeration  of  Milk.     Vermont  Experiment  Station,  Sixth 
Annual  Report. 

30.  Aeration  of  Milk  for  Butter  Production.     Indiana  Ex- 
periment Station,  Bulletin  No.  44. 

31.  "Soapy"  Milk,  and  the  Sources  of  Bacteria  in  Milk. 
Weigmann  and  Zirn :  Milch  Zeitung,  23,  1893. 

32.  The  Care  and  Handling  of  Milk.    Michigan  Experiment 
Station,  Bulletin  No.  221. 

33.  Aeration    of    Milk.     ,  Michigan    Experiment    Station, 
Special  Bulletin  No.  16. 


174  DAIRY  CHEMISTRY 

34..  Ropiness    in    Milk.      Michigan    Experiment    Station, 
Bulletin  No.  140. 

35.  Economical  Methods  for  improving  the  Keeping  Quali- 
ties of  Milk.     Maryland  Experiment  Station,  Bulletin  No.  88. 

36.  Classification  of  Dairy  Bacteria.     (Storrs)  Connecticut 
Experiment  Station  Report,  1899. 

37.  The  Comparative  Growth  of  Different  Species  of  Bacte- 
ria in  Normal  Milk.     (Storrs)  Connecticut  Experiment  Station 
Report,  1901. 

38.  Efficiency  of  a  Covered  Pail  in  excluding  Filth  and  Bac- 
teria from   Milk.     (Storrs)    Connecticut   Experiment   Station 
Report,  1901. 

39.  Dairy  Conditions   and   Suggestions  for   their  Improve- 
ment.    Illinois  Experiment  Station,  Bulletin  No.  84. 

40.  Methods  of  controlling  Contamination  of  Milk  during 
Milking.     Nebraska  Experiment  Station,  Bulletin  No.  87. 

41.  Ropiness  in  Milk  and  Cream.     New  York  (Cornell)  Ex- 
periment Station,  Bulletins  Nos.  165  and  195. 

42.  Investigations  concerning  the  Germicidal  Action  in  Cow's 
Milk.  New  York  (Cornell)  Experiment  Station,  Bnlletin  No.  197. 

43.  The  Care  and  Handling  of  Milk.     New  York  (Cornell) 
Experiment  Station,  Bulletin  No.  203. 

44.  Stagnant  Water  Germs  in  Milk.     Oregon  Experiment 
Station,  Bulletin  No.  71. 

45.  Investigations  of  Methods  of  Milking.     Wisconsin  Ex- 
periment Station,  Twentieth  Annual  Report. 

46.  Thermal  Death  Point  of  Tubercle  Bacilli  under  Com- 
mercial  Conditions.     Wisconsin   Experiment    Station,   Seven- 
teenth Annual  Report. 

47.  Outbreak  of  Anthrax  Fever  traceable  to  Tannery  Refuse. 
Wisconsin  Experiment  Station,  Seventeenth  Annual  Report. 

48.  The  Effect  of  Different  Stable  Temperatures  upon  the 
Milk  Yield  of  Dairy  Cows.     Wisconsin  Experiment  Station, 
Twenty-first  Annual  Report. 

49.  Infectiousness  of  Milk  from  Tubercular  Cows.     Wiscon- 
sin Experiment  Station,  Twenty-first  Annual  Report. 


APPENDIX  175 

50.  Effect  of  Short  Periods  of  Exposure  to  Heat  on  Tubercle 
Bacilli  in  Milk.  Wisconsin  Experiment  Station,  Twenty-first 
Annual  Report. 

REFERENCES  TO   CHAPTER   IX 

1.  The  Content  of  Pepton  in  Milk.     Schmidt  and  Miilheim  : 
Reported  in  Konig,  Cheinie  der  Menschlichen  Nahrungs-  und 
Genussmittel,  Band  II. 

2.  The  Proteids  of  Milk.     Halliburton:   Journal  of  Physi- 
ology, 2,  459. 

3.  The  Chemistry  of  Casein  and  the  Theory  of  the  Curdling 
Action  of  Rennet.     G.  Courant :  Abstract  in  Experiment  Sta- 
tion Record,  5. 

4.  Three  Forms  of  the  Casein  in  Milk.     Struve :  Journal  fur 
practische  Chemie,  1884. 

5.  The  Action  of  Rennet  on  Milk.     Hammarsten :  Popular 
Form  given  in  Milk,  its  Nature  and  Composition  by  Aikman. 

6.  The  Curdling  of  Milk  by  Ferments  which  render  the  Milk 
Alkaline.      Warrington :    Journal    of    the    Chemical    Society 
(England),  1888. 

7.  A  Study  of  the  Coagulating  Power  of  Commercial  Ren- 
nets.    Patrick :  Abstract  in  Experiment  Station  Record,  5, 100. 

8.  The  Isolation  of  Rennet  from  Bacteria  Cultures.     Conn  : 
(Storrs)  Connecticut  Experiment  Station,  Fifth  Annual  Report. 

9.  The  Nature  of  Rennet.    Russell :  Outlines  of  Dairy  Bacte- 
riology. 

10.  Beitrage  zur  Erfarschung  der  Kaserifange.     Baumann : 
Die  Landwirtschaftlichen  Versuchs-Stationen,  42,  et  seq. 

11.  Cheese-making,  Directions  for.    Iowa  Experiment  Sta- 
tion, Bulletins  Nos.  19  and  21. 

12.  Cheese  Factory  Notes.    Wisconsin  Experiment  Station, 
Annual  Report,  1892. 

13.  Cheese-making.     Article  relating  to  Recent  Work  on 
Dairying.    Allen :  Experiment  Station  Record,  5.    Nos.  10  and 
11. 

14.  Cheddar  Cheese-making.    Decker. 


176  DAIEY  CHEMISTRY 

15.  A,  B,  C  in  Cheese-making.     Monrad. 

16.  Cheese-making  in  Switzerland.     Monrad. 

17.  The  Manufacture  and  Production  of  Cheese.     Alvord : 
United  States  Department  of  Agriculture,  Year  Book,  1895. 

18.  The  Manufacture  of   Some   Fancy  Brands   of    Cheese. 
Luschinger :  Report  Sixteenth  Annual  Convention  of  the  Min- 
nesota Dairy  Association. 

19.  The  Changes  during  the  Ripening  of  Cheese.     Iowa  Ex- 
periment Station,  Bulletin  No.  24. 

20.  Salt  and  its  Preventing  the  Swelling  of  Cheese.     Von 
Freudenreich  :  Abstract  in  Experiment  Station  Record,  Vol.  V, 
p.  921. 

21.  The   Forms  of  the    Nitrogen   Compounds    in    Cheese. 
Stutzer :  Reported  in  Wiley's  Agricultural  Analysis,  Vol.  III. 

22.  Manufacture  of  Sweet  Curd  Cheese.     Haecker :  Minne- 
sota Experiment  Station,  Bulletin  No.  35. 

23.  Experiments  in  Cheese-making.    Minnesota  Experiment 
Station,  Bulletin  No.  19. 

24.  Cheese-making,  Distribution  of  Ingredients,  and  Losses 
of  Fat.     Handbook  of  Experiment  Station  Work. 

25.  Losses  in  Cheese-making.     Vermont  Experiment  Station, 
Fifth  Annual  Report. 

26.  Experiments   in   Cheese-making.     Ontario  Agricultural 
College  Report,  1894. 

27.  Losses  of  Milk  Solids  in  Cheese-making,  and  the  Addi- 
tion of  Cream  to  the  Milk.     Minnesota  Experiment  Station, 
Bulletin  No.  19. 

28.  Determining  the  Amount  of  Fat  in  Cheese  by  the  Bab- 
cock  Test.     Wisconsin  Experiment  Station,  Bulletin  No.  36. 

29.  Composition  of  Different  Kinds  of  Cheese  made  in  Dif- 
ferent  Countries.      Kdnig :    Chemie   der    Menschlichen   Nah- 
rungs-  und  Genussmittel,  Band  II. 

30.  The  Composition  of  English  Cream  Cheese.      (Cream 
added  to  the  Milk.)     P.  Vieth :  Milch  Zeitung,  1887,  120. 

31.  The  Composition  of  Milk,  Cheese,  and  Whey,  in  Relation 
to  One  Another.     Ontario  Agricultural  College  Report,  1894. 


APPENDIX  177 

32.  The  Composition  of  Cheese  made  from  Cream.    Hassall : 
Foods,  Adulterations  and  the  Methods  for  their  Detection. 

33.  The  Composition  of  Cheese.     Connecticut  State  Experi- 
ment Station  Report,  1892. 

34.  Ripen  ing  of  Cheese.    Adametz  :  Berlin.    Landwirtschaft- 
licher  Jahrbiicher,  1889. 

35.  The  Abnormal  Ripening  of  Cheese.      Adarnetz:    Milch 
Zeitung,  Nos.  21  and  22,  1892  and  1893. 

36.  An  Aromatic  Bacillus  in  Cheese.     Iowa  Experiment  Sta- 
tion, Bulletin  No.  21. 

37.  Influence  of   Cold  Curing   on   the  Quality  of  Cheddar 
Cheese  (Second  Paper).    Wisconsin  Experiment  Station,  Nine- 
teenth Annual  Report. 

38.  Influence  of  Temperatures  approximating  60°  F.  on  the 
Development  of  Flavor  in  Cold-cured  Cheese.     Wisconsin  Ex- 
periment Station,  Nineteenth  Annual  Report. 

39.  Investigations  relating  to  the  Manufacture,  Curing,  and 
Handling  of  Cheese.     See  Wisconsin  Experiment  Station,  Sev- 
enteenth, Eighteenth,  Nineteenth,  Twentieth,  and  Twenty-first 
Annual  Reports. 

40.  Investigations  relating  to  the  Manufacture,  Curing,  and 
Handling  of  Cheese.     See  New  York  State  Agricultural  Ex- 
periment Station,  Bulletins  Nos.  37,  43,  45,  46,  56,  65,  68,  110, 
184,  203,  207,  214,  215,  219,  231,  233,  234,  236,  237,  245,  and  261. 

REFERENCES   TO   CHAPTER   X 

1.  The  Composition  of  the  Milk  of  the  Mare,  Ewe,  Goat, 
Sow,  etc.      Konig :    Chemie  der  Menschlichen  Nahrungs-und 
Genussmittel,  Band  II. 

2.  Composition  of  Mule's  Milk.    Aubert  and  Colby :  Journal 
of  Analytical  and  Applied  Chemistry,  7,  No.  6. 

3.  Analyses  of  Skim-milks.     Wisconsin  Experiment  Station, 
Annual  Report  for  1889. 

4.  The  Composition  of  Whey.     New  York  State  Experiment 
Station,  Bulletins  Nos.  37,  43,  45,  46,  47. 

N 


178  DAIRY  CHEMISTRY 

5.  The  Composition  of  Buttermilk.    Maine  Experiment  Sta- 
tion, Annual  Report  for  1890. 

6.  The  Composition  of  Skim-milk  and  Whey.    C.  B.  Cochran  : 
Journal  of  the  American  Chemical  Society,  15,  No.  6. 

7.  The  Feeding  Value  of  Skim-milk.     Massachusetts  State 
Experiment  Station,  Annual  Reports  for  1884, 1885, 1886, 1887, 
18S8,  1889,  etc. 

8.  The  Effects  of  Skim-milk  in  a  Ration  for  Pigs.     Maine 
Experiment  Station,  Annual  Report  for  1889. 

9.  The  Feeding  Value  of  Skim-milk.     Vermont  Experiment 
Station,  Bulletin  No.  18. 

10.  The  Effects  of  Skim-milk  in  a  Ration  for  Pigs.     New 
Hampshire  Experiment  Station,  Bulletin  No.  11. 

11.  The  Comparative  Feeding  Value  of  Skim-milk  and  But- 
termilk.    Wisconsin  Experiment  Station,  Annual  Report  for 
1886. 

12.  The  Comparative  Feeding  Value  of  Buttermilk  and  Skim- 
milk.     Massachusetts  State  Experiment  Station,  Annual  Re- 
ports for  1884,  1885. 

13.  The  Comparative  Value  of  Sweet  and  Sour  Skim-milk. 
Vermont  Experiment  Station,  Annual  Report  for  1891. 

14.  The  Feeding  Value  of  Whey.     Wisconsin  Experiment 
Station,  Bulletin  No.  27. 

15.  The    Average   Composition   of   Skim-milk,   Buttermilk, 
and  Whey.     Konig:   Chemie  der  Menschlichen  Nahrungs-  und 
Genussmittel,  Band  II. 

16.  Influence  of  Temperature  on  Skim-milk  Tests.     Wiscon- 
sin Experiment  Station,  Seventeenth  Annual  Report. 

REFERENCES  TO   CHAPTER  XI 

1.  A  New  Milk  Test  (Beimling's).    Vermont  Experiment 
Station,  Bulletin  No.  24. 

2.  Determining  the  Fat  in  Milk.    Leffmann  and  Beam  :  Ana- 
lyst, 18,  193. 

3.  Acid  Butyrometer.     Gerber :  Chemiker  Zeitung,  16,  839. 


APPENDIX  179 

4.  The  Lactocrite.     United  States  Department  of  Agricul- 
ture, Division  of  Chemistry,  Bulletin  No.  13. 

5.  The  Lactocrite.     Biedermann's  Centralblatt,  17,  627. 

6.  A  New  Method  for  detecting  the  Fat  in  Milk.     Short: 
Wisconsin  Experiment  Station,  Bulletin  No.  16. 

7.  The   Determining  of   Fat   in   Milk    by  Short's  Method. 
Journal  of  Analytical  Chemistry,  2,  Part  4. 

8.  Cochran's  Method   for   determining   the    Fat    in    Milk. 
Journal  of  Analytical  Chemistry,  3,  Part  4. 

9.  A  Description  of  Cochran's  Method  for  determining  the 
Fat  in  Milk.     Cornell  University  Experiment  Station,  Bulletin 
No.  17. 

10.  Methods  of  manufacturing  Butter  Substitutes;  Whole- 
someness  of    Artificial  Butter ;    The   Adulteration  of  Butter, 
including  References  and  Methods  of  Analysis.    Wiley :  United 
States   Department   of    Agriculture,    Division    of    Chemistry: 
Foods  and  Food  Adulterants,  Part  First,  Dairy  Products. 

11.  Extent  and  Character  of  Food  Adulterations.     Wedder- 
burn:    United  States  Department  of  Agriculture,  Division  of 
Chemistry,  Bulletins  Nos.  25  and  32. 

12.  The   Analysis  and   Adulteration   of   Foods.     Part  III. 
James  Bell. 

13.  The  Adulteration  of  Butter  and  Cheese.     Blyth  :  Foods. 
Their  Composition  and  Analysis. 

14.  Influence  of  Preservatives  upon  the  Food  Value  of  Milk. 
Maryland  Experiment  Station,  Bulletin  No.  86. 

15.  State  and  Municipal  Milk  Legislation.     Delaware  Ex- 
periment Station,  Bulletin  No.  43. 

16.  Butter,  its  Composition,  Artificial  Imitation,  and  Adul- 
terants.   North  Carolina  Experiment  Station,  Bulletin  No.  166. 

17.  Process    Butter.     A   Dairy   Fraud.     Utah   Experiment 
Station,  Bulletin  No.  79. 

18.  Inspection  of  Milk  Tests  and  Feeding  Stuffs.     Vermont 
Experiment  Station,  Bulletin  No.  68. 

19.  Official  Tests  of  Dairy  Cows,  1903-4.    Wisconsin  Experi- 
ment Station,  Twenty-first  Annual  Report. 


180  DAIRY  CHEMISTRY 

20.  Reports  of  the  following  State  Dairy  and  Food  Commis- 
sioners :  Minnesota,  Michigan,  Illinois,  North  Dakota,  Connec- 
ticut, Kentucky,  and  other  states. 

21.  Dairy  and  Milk  Inspection.    Alabama  Experiment  Sta- 
tion, Bulletin  No.  97. 

KEFERENCES  TO  CHAPTER  XII 

1.  The  Action  of  Heat  on  Milk.     Richmond :  Analyst,  June, 
1893. 

2.  The  Sterilization  of  Milk  on  a  Large  Scale.     Hesse :  Zeit- 
schrift  fur  Hygiene,  1890,  85. 

3.  The  Chemical  and  Physical  Changes  attendant  upon  the 
Sterilization  of  Milk.     Leeds :  Journal  of  the  American  Chem- 
ical Society,  13,  No.  1. 

4.  Methods  of  Milk  Preservation.     Weigmann. 

5.  The    Pasteurization  of  Skim-milk.     Lunde:    Abstract  in 
Experiment  Station  Record,  4,  383. 

6.  Methods  of  Sterilizing  and  Pasteurizing  Milk.    Review  of 
Kinds  of  Apparatus  Used.     Allen:     Article  in  Recent  Work 
on  Dairying.     Experiment  Station  Record,  5,  1051. 

7.  Pasteurization  and  Milk  Preservation,  with  a  Chapter  on 
Selling  Milk.     Monrad. 

8.  Preservation  of  Milk.     Blyth  :  Foods. 

9.  Experiments   in   preserving  Milk   Samples.     Newmann : 
Milch  Zeitung,  22,  93. 

10.  Preservatives  and  their  Importance  in  Dairying.    Kruger : 
Molkerei  Zeitung,  1892,  No.  34. 

11.  The  Composition  of,  and  Objections  to  the  Use  of,  Preserv- 
atives in  Milk.     Current  numbers  of  the  Analyst,  1890-91,  etc. 

12.  Compilation  of  Analyses  of  Condensed  Milks.     Konig: 
Chemie  der  Menschlichen  Nahrungs-  und  Genussmittel,  Band  II. 

13.  Variations  in  the  Composition  of  Milk  during  Delivery. 
Vieth  :  Analyst,  1891  and  1892. 

14.  Standard   Milk.     New  Hampshire  Experiment  Station, 
Bulletin  No.  103. 


APPENDIX  181 

15.  The  Value  of  a  Pound  of  Milk  Solids  in  Milk  Poor  and 
Rich  in  Fat  Content.     (Storrs)  Connecticut  Report,  1904. 

16.  The  Comparative  Digestibility  of   Raw,  Pasteurized,  and 
Cooked  Milk.     Maryland  Experiment  Station,  Bulletin  No.  77. 

17.  Standard  Milk  and  Cream.    Illinois  Experiment  Station, 
Bulletin  No.  74. 

18.  City  Milk  Supply.     Illinois  Experiment  Station,  Bulle- 
tin No.  92. 

19.  Domestic  Pasteurizing  Methods  and  the  Care  of  Milk  in 
the   Home.     New  Jersey   Experiment   Station,   Bulletin    No. 
152. 

20.  The  Efficiency  of  a  Continuous  Pasteurizer  at  Different 
Temperatures. 

21.  Pasteurization    of   Skim   Milk.     Wisconsin  Experiment 
Station,  Twentieth  Annual  Report. 

22.  Pasteurization  as  applied  to  Butter-making.     Wisconsin 
Experiment  Station,  Twentieth  Annual  Report. 

23.  Preservation  of  Milk  for  Direct  Use  by  Pasteurization. 
Wisconsin  Experiment  Station,  Twentieth  Annual  Report. 

24.  On  the  Increased  Resistance  of  Bacteria  in  Milk  Pasteur- 
ized in  Contact  with  the  Air.     Wisconsin  Experiment  Station, 
Eighteenth  Annual  Report. 

25.  Estimation  of  Fat  in  Sweetened  Condensed  Milk  by  the 
Babcock    Test.     Wisconsin   Experiment   Station,  Seventeenth 
Annual  Report. 

26.  Effect  of  Pasteurization  and  Sterilization  on  the  Viscos- 
ity and  Fat  Globules  of  Milk  and  Cream.     Wisconsin  Experi- 
ment Station,  Twentieth  Annual  Report. 

27.  Restoration  of  the  Consistency  of  Pasteurized  Milk  and 
Cream.     Wisconsin  Experiment   Station,   Twentieth   Annual 
Report. 

KEFEKENCES   TO   CHAPTER   XIII 

1.  The  Composition  of  Butter-fat  as  affected  by  Food.     New 
Hampshire  Experiment  Station,  Bulletins  Nos.  16  and  18. 

2.  Effect  of  Food  upon  the  Quality  of  Butter.     Article  on 


182  DAIRY  CHEMISTRY 

Butter-making   in   Handbook   of   Experiment   Station   Work. 
United  States  Department  of  Agriculture. 

3.  Effect  of  Cotton-seed  Meal  on  the  Composition  of  Butter. 
Texas  Experiment  Station,  Bulletins  Nos.  11  and  14. 

4.  Effect  of  Cotton-seed  Meal  on  Butter.    Alabama  (College) 
Experiment  Station,  Bulletin  No.  25. 

5.  Injurious  Effects  of  Certain  Plants  on  Milk  and  its  Prod- 
ucts.    Milch  Zeitung,  1892,  46. 

6.  The  Effect  of  Peanut  Cake  and  Cotton-seed  Cake  on  the 
Fat  Content  of  Milk.     Backaus :  Journal  fur  Landwirtschaft, 
41,  4. 

7.  Effects   of   Different   Kinds   of   Food   upon   Butter.     A. 
Mayer:  Die  Landwirtschaftlichen  Versuchs-Stationen,  41. 

8.  Influence  of   Food   upon    the   Qualities    of   Butter   Fat. 
Frear :  Agricultural  Science,  1833,  7. 

9.  Transmission  of  Nitrates  to  Milk.     Richmond:  Analyst, 
1893,  279. 

10.  On  the  Effect  of  feeding  Fat  to  Cows.     Wing :  Cornell 
University  Experiment  Station,  Bulletin  No.  92. 

11.  Recovery  of  the  Food  Ingredients  in  the  Milk.     New 
York  State  Experiment  Station  Report,  1891. 

12.  Effects  of  Rye  Pasture  on  the  Taste  of  Milk.     Breeder's 
Gazette,  26,  203,  220,  239. 

13.  Transmission  of  Substances  from  Food  to  Milk.    Froh- 
ner:  Zeitschrift  fiir  Fleisch  und  Milch  Hygiene,  10,  1. 

14.  Influence  of  the  Quality  of  Food  upon  the  Economy  of 
Milk  and  Butter  Production.     Pennsylvania  Experiment  Sta- 
tion, Annual  Report  for  1895. 

15.  Quality  of  Butter  as  influenced  by  Food.     Pennsylvania 
Experiment  Station,  Bulletin  No.  17. 

16.  Influence  of   Roots  and   Silage  on  the  Composition  of 
Milk.     Pennsylvania  Experiment  Station  Report,  1890. 

17.  The  Quality  of  Butter  as  affected  by  Food.     Maine  Ex- 
periment Station  Report,  1891. 

18.  Simple  Methods  of  determining  Milk  Fat  (Short's  and 
Cochran's).    Pennsylvania  Experiment  Station,  Bulletin  No.  12. 


APPENDIX  183 

19.  Failyer  and  Willard's  Method  for  determining  the  Fat 
in  Milk.    Journal  of  Analytical  Chemistry,  3,  Part  3. 

20.  Parsons'  Method    for  determining    the    Fat   in    Milk. 
Journal  of  Analytical  Chemistry,  3,  Part  3. 

21.  The  Oil  Test  for  Cream.    Wis.  Ex.  Sta.,  Bui.  12. 

22.  Patrick's  Method  of  testing  Milk.    Iowa  Experiment 
Station,  Bulletins  Nos.  8  and  11. 

23.  Milk   Tests,   Comparison   of  Simple  Methods.    Illinois 
Experiment  Station,  Bulletins  Nos.  10  and  14. 

24.  Comparison  of  Various  Methods  for  testing  Milk.     West 
Virginia  Experiment  Station,  Third  Annual  Report. 

25.  Milk  Tests.     Handbook  of   Experiment  Station  Work, 
United  States  Department  of  Agriculture. 

26.  Feser's  Lactoscope.     Die  Lands.  Vers.-Stat.,  27,  2,  135. 

27.  The  Lactoscope.     Biedermann's  Centralblatt,  9,  302. 

28.  Effects  of  Feed  upon  the  Quality  of  Milk.     Iowa  Experi- 
ment Station,  Bulletins  Nos.  13,  14,  16,  17. 

29.  A  Study  of  Milk  Secretion.     (Storrs)  Connecticut  Ex- 
periment Station  Report,  1904. 

30.  The  Effect  of  Silage  on  the  Acidity  of  Milk.     (Storrs) 
Connecticut  Experiment  Station  Report,  1904. 

31.  Weedy  Flavors  in  Butter.     California  Experiment  Sta- 
tion, Annual  Report,  1903. 

32.  Studies  in  Milk  Secretion.    New  York  (Cornell)  Experi- 
ment  Station,  Bulletins  Nos.  152  and  169. 

33.  The  Relation  of  Food  to  Milk  Fat.     New  York  (Cornell) 
Experiment  Station,  Bulletin  No.  173. 

34.  Methods  of  Milking.     New  York  (Cornell)  Experiment 
Station,  Bulletin  No.  213. 

35.  Record  of  an  Attempt  to  increase  the  Fat  in  Milk  by 
Means  of  Liberal  Feeding.     New  York  (Cornell)  Experiment 
Station,  Bulletin  No.  222. 

36.  The  Source  of  Milk  Fat.     New  York  State  Experiment 
Station,  Bulletin  No.  132. 

37.  Flavors   in  Milk   and  its  Products.     New  York  State 
Experiment  Station,  Bulletin  No.  183- 


184  DAIRY  CHEMISTRY 

38.  Fat  in  Milk  from  Starch  in  Food.     New  York  State  Ex- 
periment Station,  Bulletin  No.  197. 

39.  The  Immediate  Effect  on  Milk  Production  of  Changes  in 
the  Ration.     New  York   State   Experiment   Station,  Bulletin 
No.  210. 

40.  The    Effect   of   Food   on   Economic   Dairy   Production. 
Texas  Experiment  Station,  Bulletin  No.  47. 

41.  A  Study  of  Butter  Increasers.     Iowa  Experiment  Station, 
Bulletin  No.  52. 

REFERENCES   TO   CHAPTER   XIV 

[NOTE.  —  The  literature  on  this  subject  is  so  extensive  that  only  a 
few  typical  references  are  given.  For  references  to  special  topics,  as 
the  characteristic  value  of  any  food  for  milk  production,  the  student  is 
referred  to  the  card  catalogue  index  issued  by  the  United  States  De- 
partment of  Agriculture,  Office  of  Experiment  Stations.  In  calculat- 
ing rations,  it  is  best  to  use  the  figures  given  for  the  average  composi- 
tion of  American  feeding  stuffs,  except  in  those  cases  where  extended 
special  investigations  have  been  made  of  the  fodders  of  a  state  by  an 
Experiment  Station.] 

1.  Manual  of  Cattle  Feeding.     Armsby. 

2.  Landwirtschaftliche  Futterungslehre.     Ernil  Wolff. 

3.  Feeding   Farm   Animals.      Allen:  Office  of   Experiment 
Stations,  United  States  Department  of  Agriculture,  Farmer's 
Bulletin  No.  22. 

4.  A  Compilation  of  Analyses  of  American  Feeding  Stuffs. 
Jenkins  and  Winton :    Office  of  Experiment  Stations,  United 
States  Department  of  Agriculture,  Bulletin  No.  38. 

5.  One  Hundred  American  Rations  for  Dairy  Cows.     Woll : 
Wisconsin  Experiment  Station,  Bulletin  No.  38. 

6.  Investigation  in  Milk  Production  ;  Feeding  Dairy  Cows. 
Minnesota  Experiment  Station,  Bulletins  Nos.  71  and  79. 

7.  Feeding  Experiments  with   Dairy  Cows.     Alabama  Ex- 
periment Station,  Bulletin  No.  114. 

8.  Feed  and  Care  of  the  Dairy  Cow.      Kansas  Experiment 
Station,  Bulletin  No.  81. 


APPENDIX  185 

9.  Ration  Tests  for  Dairy  Cows ;  the  Best  Week  in  a  Cow's 
Lactation    Period.      Nebraska   Experiment    Station,    Bulletin 
No.  76. 

10.  Discussion  of  the  Amount  of  Protein  required  in   the 
Ration    for  Dairy   Cows.      (Storrs)    Connecticut    Experiment 
Station   Report,  1904. 

11.  A  Study  of  Rations  fed  to  Milch  Cows  in  Connecticut. 
(Storrs)  Connecticut  Experiment  Station  Report,  1900. 

12.  A  Study  of  Rations  fed  to  Milch  Cows.     (Storrs)  Con- 
necticut Experiment  Station  Report,  1901. 

13.  Economic  Feeding  of  Milch  Cows.     (Hatch)  Massachu- 
setts Experiment  Station,  Bulletin  No.  39. 

14.  Rations  for   Milch   Cows.     Rhode   Island    Experiment 
Station,  Bulletin  No.  77. 

15.  Individuality  of  Cows.     Rhode  Island  Experiment  Sta- 
tion, Bulletin  No.  80. 

16.  Feeding  Dairy  Cows.     Michigan  Experiment  Station, 
Bulletin  No.  149. 


INDEX 


Abnormal  creams,  churning  of,  65. 

Absorption  of  odors  by  milk,  78. 

Acid,  adding  of,  to  milk,  16; 
butyric,  31;  disposal  of,  waste, 
23;  handling  of,  23;  lactic, 
production  of,  44;  measure,  17; 
strong,  22 ;  weak,  22. 

Acidity,  calculation  of,  in  milk, 
47;  of  cream,  49;  of  milk,  47. 

Acids,  fatty,  31 ;  volatile  fatty,  33. 

Adulteration  of  butter,  112;  of 
cream,  58;  of  milk,  41. 

Aerating  milk,  86. 

Albumin,  5,  89;  coagulation  of,  5. 

Alkali,  standard,  47. 

Alkaline  tablets,  48. 

Apparatus,  care  of,  28. 

Ash,  6. 

Ash  of  foods,  132. 

Babcock's  formula,  40. 

Babcock  test,  13-28;  reliability  of, 

13. 

Balanced  rations,  influence  of,  129. 
Bartlett  test  bottle,  51. 
Boric  acid  in  milk,  113. 
Butter,  adulterations  of,  112 ;  color, 

70;  composition  of,  69;  fats,  29; 

hard,  29;  judging,  73;    melting 

point,  34;   renovated,  113;  soft, 

29;  working  of ,  66. 
Buttermilk,  composition  of,  67. 
Butters,  hard,  production  of,  126 ; 

soft,  production  of,  127. 
Butyric  acid,  31. 
Butyrin,  31. 
By-products  of  milk,  107. 


Calculation  of  acidity  in  milk,  47; 
-of  rations,  139. 


Calibration  of  test  bottles,  19. 

Caloric  value  of  foods.  136. 

Carbohydrates,  of  foods,  134. 

Care  of  dairy  utensils,  80 ;  of  milk 
rooms,  81;  of  test  bottles  and 
apparatus,  28. 

Casein,  5,  89. 

Centrifugal  action,  21. 

Centrifuge,  17 ;  action  of,  21 ;  speed- 
ing of,  20. 

Cheddar  cheese,  92. 

Cheese,  composition  of,  101 ;  differ- 
ent kinds  of,  104;  filled,  114; 
making,  88-106 ;  quick-ripening, 
97 ;  slow-curing,  97 ;  skim  milk, 
114;  testing  of,  100;  yield  of 
milk,  99. 

Churning,  62 ;  abnormal  creams, 
65;  exhaustive,  65;  and  grain 
of  butter,  65;  influence  of  food 
on,  64;  influence  of  ripeness  of 
cream  on,  63 ;  influence  of  season 
on,  64;  influence  of  temperature 
on,  64;  thick  and  thin  cream,  64. 

Cleaning  glassware,  27. 

Coarse  fodders,  influence  of,  in  ra- 
tions, 127. 

Cochrane,  method  of,  117. 

Cold  curing  of  cheese,  98. 

Cold  deep  setting,  55. 

Color  of  milk,  70. 

Colostrum  milk,  83. 

Composite  sample,  24. 

Composition  of  butter,  69 ;  of  but- 
termilk, 67;  of  fats,  29;  of 
fodders,  148-149;  of  grains,  147; 
of  milk,  1-12;  of  milk,  individ- 
ual cows,  8,  9. 

Condensed  milk,  123. 

Corn,  influence  of,  on  butter,  136. 


187 


188 


INDEX 


Cost  and  value  of  foods,  144. 

Cottage  cheese,  105. 

Cotton-seed  meal,  influence  of,  on 
butter,  126. 

Cream,  49-61 ;  acidity  of,  49;  adul- 
teration of,  59 ;  amount  of,  from 
milk,  50;  composition  of,  50; 
heating  of,  59;  raising  by  dilu- 
tion, 61 ;  ripening  of,  59 ;  separa- 
tors, 54  ;  test  bottle,  51 ;  testing, 
51 ;  thick,  50;  thin,  50;  viscosity, 
58;  weighing  of,  for  testing,  53. 

Creaming,  gravity  process,  54 ;  in- 
fluence of  delay,  60 ;  methods  of, 
54;  milk,  temperature  of,  58:  of 
mixed  milks,  61. 

Crude  fat,  135. 

Crude  fiber,  135. 

Cultures,  59. 

Curd,  grinding  of,  94. 

Curd  knife,  93. 

Curing  of  cheese,  97. 

Dairy  laws,  117. 

Dairy  salt,  66. 

Dairy  utensils,  care  of,  80. 

Delay  in  creaming,  60. 

Detection  of  the  skimming  of  milk, 

39;    of    the  watering    of    milk, 

69. 

Determination  of  lactic  acid,  45. 
Digestible  nutrients  of  foods,  138. 
Dilution,  cream  raising  by,  61. 
Disease  and  foul  air,  79. 
Dividends,  72. 
Dry  matter,  132. 

Edam  cheese,  105. 

Enzymes  and  cheese  ripening,  97. 

Exhaustive  churning,  65. 

Fat,  feeding  of,  in  ration,  126 ;  glob- 
ules, 4 ;  size  of  globules,  4 ;  losses 
of,  in  skim  milk,  57  ;  Tosses  of,  in 
butter  making,  67 ;  reading  of, 
in  test,  18. 


Fats,  composition  of,  29;  food 
value,  32;  melting  point,  34; 
milk,  3;  present  in  butter,  29; 
properties  of,  29-34;  saponifica- 
tion  of,  33 ;  specific  gravity,  34. 

Fatty  acids,  31. 

Feeding  of  dairy  stock,  144 ;  skim 
milk,  107 ;  value  of  whey,  100. 

Fermentation  of  milk  sugar,  43. 

Ferments,  lactic  acid,  43. 

Fibrin,  86. 

Filled  cheese,  114. 

First  milk,  10. 

Flavors  imparted  by  foods,  128. 

Fodders,  coarse,  influence  of,  in 
rations,  127. 

Food  value  of  milk,  123. 

Foods,  caloric  value  of,  136;  car- 
bohydrates, 134;  crude  fat  of, 
135;  crude  fiber  of,  1:35;  influence 
of,  on  butter,  127,  128 ;  selection 
of,  for  ration,  137;  uses  of,  by 
body,  131. 

Fore  milk,  10. 

Formalin  in  milk,  115. 

Formula,  Babcock's,  40;  Hehner 
&  Richmond's,  41. 

Foul  air  and  disease,  79. 

Frozen  milk,  sampling  of,  26. 

Gases  in  milk,  86. 

Gerber's  Butyrometer,  116. 

Germ  content  of  milk,  77. 

Glassware,  cleaning  of,  27. 

Globules,  fat,  4. 

Gluten    meal,    influence    of,    on 

butter,  127. 
Glycerine,  31. 
Gouda  cheese,  105. 
Grain    of   butter,    influenced    by 

churning,  65. 
Gravity  creaming,  54. 

Hard  butters,  production  of,  120. 

Heating  of  cream,  59. 

Hehner  &  Richmond's  formu'.a,  41. 


INDEX 


189 


Illegal  milk,  41. 

Indicator,  46. 

Influence  of    foods  on  quality  of 

butter,  127, 128;  of  water  on  milk 

supply,  83. 
Iodine  absorption,  33. 

Judging  butter,  73. 

Lactic  acid,  determination  of,  45; 
ferments,  43 ;  production  of,  44. 
Lactocrite,  116. 
Lactometer,  its  use,  35-42. 
Lactose,  5. 
Laws,  Dairy,  117. 
Limburger  cheese,  104. 
Loss  of  fat  in  skim  milk,  57. 
Losses  of  fat  in  butter  making,  67. 

Maintenance  ration,  131. 

Mare's  milk,  111. 

Market  milk,  119-130. 

Measuring  acid,  16;  milk,  15. 

Melting  point  of  fats,  34. 

Method  of  cheese  making,  93-94. 

Methods  of  creaming,  54. 

Milk,  absorption  of  odors  by,  78; 
acidity  of,  47;  ash,  6;  as  hu- 
man food,  123 ;  by-products,  107 ; 
changes  during  transportation, 
120;  cheese,  yield  of,  99;  color 
of,  70;  complexity  of  composi- 
tion, 1;  composition  of,  1-10; 
composition  of,  individual  cows, 
8-9;  condensed,  123;  contami- 
nated by  soil,  78 ;  fats,  3 ;  from 
diseased  animals,  76;  gases 
in,  86;  germ  content,  77;  il- 
legal, 41;  influence  of  storage 
in  stables  on,  77 ;  mixing  of 
samples,  14;  pails,  washing  of, 
80;  pasteurizing  of,  121;  pipette, 
15;  proteids,  88;  rooms,  care  of, 
81 ;  sanitary  condition  of,  75-87 ; 
secretion,  125;  serum,!;  solids, 
2  ;  solids,  calculation  of,  40 ;  spe- 


cific gravity,  36;  sterilized,  121; 
sugar,  7;  sugar,  fermentation 
of,  43;  supply,  influence  of  tu- 
berculosis, 76;  testing,  13-28; 
testing,  importance  of ,  13;  watei 
in,  2;  yields,  9;  urea  in,  76. 

Nutrients,  131. 
Nutritive  ratio,  137. 

Oats,  influence  of,  on  butter,  127. 
Oleomargarine,  112 ;  tests  for,  112. 
Organic  matter  of  foods,  133. 
Overruns,  71. 

Palmitin,  31. 
Pasteurizing  milk,  121. 
Pipette,  milk,  15. 
Potassium  bichromate,  24. 
Preservatives  in  milk,  113. 
Proteids  of  foods,  133;  of  milk,  88. 

Quick  ripening  of  cheese,  97. 

Ratio,  nutritive,  137. 
Ration,  calculation  of,  139. 
Rational  feeding,  131-146. 
References,  161-185. 
Rennet,  90;  test,  91. 
Renovated  butter,  113. 
Review  questions,  151-160. 
Ripening  of  cream,  59. 
Roots,  value  of,  in  ration,  142. 
Roquefort  cheese,  105. 

Salt,  dairy,  66. 

Samples,  mixing  of  milk,  14. 

Sampling  frozen  milk,  26;   milk, 

14. 

Sanitary  condition  of  milk,  75-87. 
Saponification  of  fats,  33. 
Secretion  of  milk,  125. 
Selection  of  foods  for  ration,  137. 
Separators,  efficiency  of,  57. 
Separator  slime,  57. 
Serum,  milk,  1. 


190 


INDEX 


Serum  solids,  11. 

Sheep's  milk,  111. 

Short,  method  of,  116. 

Silage,  influence  of,  on  butter,  128. 

Skim-milk  cheese,  114 ;  feeding  of, 
107. 

Skimming,  detection  of,  39. 

Skim  milk,  testing  of,  26, 

Slow-curing  cheese,  97. 

Soft  butters,  production  of,  127. 

Soil  contamination  of  milk,  78. 

Solids,  milk,  2;  in  milk,  calcula- 
tion of,  40 ;  not  fat,  11. 

Sow's  milk,  111. 

Specific  gravity  of  fats,  34;  of 
milk,  36;  of  skim  milk,  37. 

Stables,  sanitary  condition  of,  77 ; 
storing  milk  in,  77 ;  ventilation 
of,  79. 

Standard  alkali,  47;  ration,  138. 

Stearin,  31. 

Sterilizing  milk,  121. 

Stilton  cheese,  104. 

Strippings,  10. 

Sugar,  7. 

Sulphuric  acid,  22. 

Sweet  and  sour  cream,  churning  of, 
64. 

Swiss  cheese,  104. 

Tables  of  composition  of  foods, 
147-149 ;  for  correcting  lactome- 
ter readings,  150. 

Tablets,  alkaline,  48. 

Temperature  of  creaming  milk,  58; 
of  churning,  64;  influence  of,  on 
lactometer,  37. 

Test,  rennet,  91. 

Test  bottles,  17;   calibration  of, 


19;  care  of,  28;  for  cream,  51; 

for  skim  milk,  26 ;  whirling  of, 

18. 
Testing  cheese,    100;    cream,  51; 

milk,      12-28 ;     importance     of 

milk,  13;  skim  milk,  26;  whey, 

102. 

Tests  for  oleomargarine,  112. 
Thick  and  thin  cream,  churning  of, 

64. 
Transportation  of  milk,   changes 

during,  120. 

Tuberculosis  and  milk  supply,  76. 
Tyrotoxicon,  85. 

Urea  in  milk,  76. 

Use  of  pipette,  15. 

Uses  of  food  by  body,  131. 

Value  and  cost  of  foods,  144. 
Ventilation  of  stables,  79. 
Viscosity  of  cream,  58. 
Volatile  fatty  acids,  33. 

Water,  addition  of,  to  test  bottles, 
18;  in  butter,  69;  influence  of, 
on  milk  supply,  83;  in  milk,  2. 

Watering  of  milk,  detection  of, 
39. 

Weighing  cream  for  testing,  52. 

Wheat  by-products,  influence  of, 
on  butter,  127. 

Whey,  testing  of,  102;  value  for 
feeding,  100. 

Whirling  test  bottles,  18. 

Wiuton  test  bottle,  51. 

Working  butter,  66. 

Yields,  milk,  9. 


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